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 93.04348% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 79.15%. Comparing base (e147aaa) to head (9956264).

Files with missing lines	Patch %	Lines
devito/ir/iet/visitors.py	75.00%	14 Missing ⚠️
devito/operator/operator.py	75.86%	5 Missing and 2 partials ⚠️
tests/test_specialization.py	99.10%	1 Missing and 1 partial ⚠️
devito/ir/support/guards.py	85.71%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2812      +/-   ##
==========================================
+ Coverage   79.05%   79.15%   +0.09%     
==========================================
  Files         248      249       +1     
  Lines       51276    51602     +326     
  Branches     4431     4450      +19     
==========================================
+ Hits        40534    40843     +309     
- Misses       9932     9949      +17     
  Partials      810      810              

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.