Improve SymFiniteBits interface

[lsrcz]

This pull request makes symCountLeadingZeros/symPopCount/symCountTrailingZeros less confusing by returning the arg type. Previously, it will return a literal value when we return a dynamic-sized bit vector (SomeBV) without the bit-width assigned. This can be confusing and is very hard to debug.

This pull request ensures that the bit-width is always adequately assigned.

[codecov]

Codecov Report

Attention: Patch coverage is 50.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 54.74%. Comparing base (6dd4e9b) to head (318d91f).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...isette/Unified/Internal/Class/UnifiedFiniteBits.hs	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #262      +/-   ##
==========================================
+ Coverage   54.67%   54.74%   +0.06%     
==========================================
  Files         121      121              
  Lines       12914    12914              
  Branches      910      907       -3     
==========================================
+ Hits         7061     7070       +9     
+ Misses       4943     4937       -6     
+ Partials      910      907       -3     

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