Simplify the instances for uninterpreted functions and fix the missing instances for concrete functions

[lsrcz]

This pull request simplifies the instances for uninterpreted functions by moving the constraints to the types themselves as GADTs.

This pull request also fixes the missing instances for concrete functions, especially the ITEOp/SimpleMergeable/Mergeable instances for general functions.

[codecov]

Codecov Report

Attention: Patch coverage is 30.70866% with 88 lines in your changes missing coverage. Please review.

Project coverage is 53.48%. Comparing base (85bc615) to head (6ea4113).
Report is 3 commits behind head on main.

Files	Patch %	Lines
src/Grisette/Internal/SymPrim/GeneralFun.hs	36.14%	53 Missing ⚠️
src/Grisette/Internal/Core/Data/Class/SubstSym.hs	0.00%	8 Missing ⚠️
src/Grisette/Internal/SymPrim/SymGeneralFun.hs	0.00%	5 Missing and 1 partial ⚠️
src/Grisette/Internal/SymPrim/SymTabularFun.hs	0.00%	5 Missing and 1 partial ⚠️
src/Grisette/Internal/Core/Data/Class/GenSym.hs	0.00%	4 Missing ⚠️
src/Grisette/Internal/Core/Data/Class/Mergeable.hs	0.00%	4 Missing ⚠️
src/Grisette/Internal/Core/Data/Class/ToCon.hs	0.00%	4 Missing ⚠️
...rc/Grisette/Internal/Core/Data/Class/ExtractSym.hs	0.00%	2 Missing ⚠️
...isette/Internal/Core/Data/Class/SimpleMergeable.hs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #249      +/-   ##
==========================================
- Coverage   53.71%   53.48%   -0.23%     
==========================================
  Files         117      117              
  Lines        9892     9980      +88     
  Branches      940      945       +5     
==========================================
+ Hits         5313     5338      +25     
- Misses       3639     3697      +58     
- Partials      940      945       +5     

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