core: Add FixedbitWidthType Interface

[jorendumoulin]

These functions to determine the bit/byte width of an element are useful in many places. I think I have them implemented in a couple of different places myself, so I think this abstraction is quite useful in this regard. The functions were now defined in a pass, I simply moved them over.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 89.90%. Comparing base (2f24609) to head (90f853c).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2904      +/-   ##
==========================================
- Coverage   89.90%   89.90%   -0.01%     
==========================================
  Files         403      404       +1     
  Lines       50422    50481      +59     
  Branches     7787     7795       +8     
==========================================
+ Hits        45333    45383      +50     
- Misses       3862     3866       +4     
- Partials     1227     1232       +5     

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