chore: remove some TODOs from codebase

[guorong009]

Description

• Take care of some TODOs throughout the repo

Related issues

Changes

• parallelize compute_inner_product utility
• use ColumnMid in QueryBack
• remove renaming in halo2_backend/plonk/permutation
• refactor the EvaluationDomain::extended_to_coeff function

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 94.82759% with 3 lines in your changes missing coverage. Please review.

Project coverage is 85.14%. Comparing base (f0a2ebd) to head (ef6f740).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
halo2_backend/src/plonk/evaluation.rs	96.42%	1 Missing ⚠️
halo2_backend/src/plonk/lookup/verifier.rs	80.00%	1 Missing ⚠️
halo2_backend/src/plonk/shuffle/verifier.rs	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #376   +/-   ##
=======================================
  Coverage   85.13%   85.14%           
=======================================
  Files          85       85           
  Lines       18862    18872   +10     
=======================================
+ Hits        16058    16068   +10     
  Misses       2804     2804           

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[adria0]

LGTM

[davidnevadoc]

LGTM! 👍