build: bump RUSTC_VERSION to 1.88 in github workflows

[joyeecheung]

The canary builds have been failing:

error: rustc 1.86.0 is not supported by the following packages:
  diplomat@0.16.1 requires rustc 1.88
  diplomat-runtime@0.15.2 requires rustc 1.88
  diplomat_core@0.16.1 requires rustc 1.88
  icu_locale_core@2.3.0 requires rustc 1.88
  icu_provider@2.3.1 requires rustc 1.88
  node_crates@15.5.1 requires rustc 1.88

make[2]: *** [deps/crates/node_crates.target.mk:13: /home/runner/work/node-v8/node-v8/node/out/Release/obj/gen//release/libnode_crates.a] Error 101

This updates the github action files to keep the rust version in line with Jenkins nodejs/build#4265

[nodejs-github-bot]

Review requested:

• @nodejs/actions

[github-actions]

Fast-track has been requested by @joyeecheung. Please 👍 to approve.

[joyeecheung]

It looks like github actions didn't recognize my base branch change. Rebased. @richardlau @aduh95 can you take a look again?

[richardlau]

(Given this is for canary, this should only be needed for future V8/temporal so I've also added dont-land-on-v26.x PRs that should not land on the v26.x-staging branch and should not be released in v26.x. .)

[MikeMcC399]

Should the minimum version in https://github.com/nodejs/node/blob/main/BUILDING.md#building-nodejs-with-temporal-support be updated as well?