compiler: Introduce operator specialization

[EdCaunt]

WIP - the intention is to allow users to build an operator as per usual, then generate single-use "specialised" versions of it with hardcoded values in the generated code to free up registers

[codecov]

Codecov Report

❌ Patch coverage is 98.71795% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.03%. Comparing base (a00cca8) to head (e70b6d5).
⚠️ Report is 15 commits behind head on main.

Files with missing lines	Patch %	Lines
devito/ir/support/guards.py	85.71%	1 Missing ⚠️
tests/test_specialization.py	99.09%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2812      +/-   ##
==========================================
+ Coverage   83.01%   83.03%   +0.01%     
==========================================
  Files         248      249       +1     
  Lines       50957    51150     +193     
  Branches     4489     4500      +11     
==========================================
+ Hits        42303    42473     +170     
- Misses       7883     7907      +24     
+ Partials      771      770       -1     

Flag	Coverage Δ
pytest-gpu-aomp-amdgpuX	68.40% <47.61%> (-0.10%)	⬇️
pytest-gpu-nvc-nvidiaX	68.94% <47.61%> (-0.08%)	⬇️

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