compiler: Tweak blocking for CPML-like subdomains and GPUs

[FabioLuporini]

Still things to tweak, but it's a start

[codecov]

Codecov Report

❌ Patch coverage is 56.66667% with 13 lines in your changes missing coverage. Please review.
✅ Project coverage is 44.87%. Comparing base (25c2dc1) to head (801a246).
⚠️ Report is 2 commits behind head on main.

Files with missing lines	Patch %	Lines
devito/passes/clusters/blocking.py	58.62%	11 Missing and 1 partial ⚠️
tests/test_dle.py	0.00%	1 Missing ⚠️

❗ There is a different number of reports uploaded between BASE (25c2dc1) and HEAD (801a246). Click for more details.

HEAD has 15 uploads less than BASE

Flag	BASE (25c2dc1)	HEAD (801a246)
	18	8
pytest-gpu-gcc-	6	2
pytest-gpu-icx-	2	1

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3007       +/-   ##
===========================================
- Coverage   79.35%   44.87%   -34.48%     
===========================================
  Files         257      257               
  Lines       54630    54654       +24     
  Branches     4682     4685        +3     
===========================================
- Hits        43352    24527    -18825     
- Misses      10415    29138    +18723     
- Partials      863      989      +126     

Flag	Coverage Δ
pytest-gpu-gcc-	43.01% <56.66%> (-35.28%)	⬇️
pytest-gpu-icx-	42.86% <56.66%> (-0.07%)	⬇️

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