feat: add middleware check_witness

[ed255]

Complete the implementation of the check_witness function which checks that a witness assignment passes all the constraints from a middleware Circuit. The missing parts were:

• Simulate blind rows
• Check copy constraints
• Check lookups
• Check shuffles

I've tried to keep the implementation simple (compared to the MockProver). For now it panics instead of returning errors.

This function was previously defined in the p3_frontend but is now moved to halo2_debug so that it can be used anywhere.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 59.52381% with 51 lines in your changes missing coverage. Please review.

Project coverage is 82.48%. Comparing base (bc857a7) to head (da4983e).

Files	Patch %	Lines
halo2_debug/src/check_witness.rs	58.19%	51 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #356      +/-   ##
==========================================
- Coverage   82.64%   82.48%   -0.17%     
==========================================
  Files          84       85       +1     
  Lines       17750    17832      +82     
==========================================
+ Hits        14670    14709      +39     
- Misses       3080     3123      +43     

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