[F2C] refactoring cgen and *c-like* codegen

[MichaelSt98]

and introducing c-like codegen (cppgen', 'cudagen)

[github-actions]

Documentation for this branch can be viewed at https://sites.ecmwf.int/docs/loki/280/index.html

[codecov]

Codecov Report

Attention: Patch coverage is 96.96970% with 5 lines in your changes missing coverage. Please review.

Project coverage is 92.89%. Comparing base (5772340) to head (962528e).
Report is 438 commits behind head on main.

Files with missing lines	Patch %	Lines
loki/backend/cgen.py	97.10%	2 Missing ⚠️
loki/backend/cudagen.py	94.59%	2 Missing ⚠️
loki/backend/cppgen.py	98.11%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #280      +/-   ##
==========================================
+ Coverage   92.82%   92.89%   +0.07%     
==========================================
  Files          98      104       +6     
  Lines       18053    18250     +197     
==========================================
+ Hits        16757    16953     +196     
- Misses       1296     1297       +1     

Flag	Coverage Δ
lint_rules	96.39% <ø> (ø)
loki	92.86% <96.96%> (+0.06%)	⬆️
transformations	92.20% <ø> (+0.19%)	⬆️

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[reuterbal]

This PR should be made redundant by #328, right?

[MichaelSt98]

This PR should be made redundant by #328, right?

That is correct, yes!