ITS: simplify parallel_for loops

[f3sch]

This just simplifies the syntax used in parallel_for loops, instead of:

tbb::parallel_for(
      tbb::blocked_range<int>(0, mTrkParams[iteration].TrackletsPerRoad()),
      [&](const tbb::blocked_range<int>& Layers) {
        for (int iLayer = Layers.begin(); iLayer < Layers.end(); ++iLayer) {

this now just

tbb::parallel_for(0, mTrkParams[iteration].TrackletsPerRoad(), [&](const int iLayer) {

which I think is much clearer. This does no functional changes.

Also after #14595, I realised I dont need to use an atomic for the level update since this part is sequential anyways.

[github-actions]

REQUEST FOR PRODUCTION RELEASES:
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[alibuild]

Error while checking build/O2/fullCI_slc9 for 8bd3b93 at 2025-09-13 03:49:

## sw/BUILD/O2-sim-challenge-test-latest/log
./trdMatch.log[16805:trd-globaltracking_TPC_FT0_ITS-TPC_CTP_]: [03:47:50][ERROR] VDriftHelper: Could not get T/P for time range 0 -> 0
./tofMatchTracks.log[18996:tof-matcher]: [03:48:29][ERROR] VDriftHelper: Could not get T/P for time range 0 -> 0
./tpcreco.log[10654:tpc-tracker]: [03:46:09][ERROR] VDriftHelper: Could not get T/P for time range 0 -> 0
./pvfinder.log[22642:pvertex-track-matching]: [03:49:29][ERROR] VDriftHelper: Could not get T/P for time range 0 -> 0
./sim-challenge.logDetected critical problem in logfile svfinder.log
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/37}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/38}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/40}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/42}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/43}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/45}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/46}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/47}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/48}
./digi.log[ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/49}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/37}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/38}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/40}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/42}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/43}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/45}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/46}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/47}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/48}
./digi.log[6183:TRDDigitizer]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/49}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/37}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/38}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/40}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/42}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/43}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/45}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/46}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/47}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/48}
./digi.log[6125:SimReader]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/49}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/37}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/38}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/40}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/42}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/43}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/45}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/46}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/47}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/48}
./digi.log[6096:internal-dpl-clock]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/49}
./digi.log[6270:TPCDigitizer_1]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/37}
./digi.log[6270:TPCDigitizer_1]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/38}
./digi.log[6270:TPCDigitizer_1]: [ERROR] Found duplicate input binding with different spec.:collisioncontext {SIM/COLLISIONCONTEXT/40}
[0 more errors; see full log]

Full log here.

[f3sch]

@fprino @mconcas, can we merge this?

[f3sch]

@mconcas can we please merge this since the macOs-arm built failure is unrelated and I anyways built on arm?