Fixing issues with comment extraction for the help string

[swansonk14]

This PR fixes two issues with comment extraction for the help string.

1. From Escaped characters in docstring are over-escaped by the tokenizer #97, escaped quote characters (e.g., "\"") in the help string are incorrectly un-escaped.

This was fixed by using a bytes representation with an ascii encoding and a unicode-escape decoding.

2. From [suggestion] Class variable arguments with multiline defaults do not respect help comments  #130, strings in multiline assign statements are parsed as comments rather than the true comment after the multiline assign statement.

Taking inspiration from #144, we the ast package to differentiate between strings belonging to an assign statement and strings intended as a comment for the help string. Thank you @arnaud-ma for the great idea!

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 82.35294% with 6 lines in your changes missing coverage. Please review.

Project coverage is 93.49%. Comparing base (5257fe8) to head (3980c81).

Files	Patch %	Lines
src/tap/utils.py	82.35%	6 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##             main     #148      +/-   ##
==========================================
- Coverage   94.07%   93.49%   -0.59%     
==========================================
  Files           4        4              
  Lines         692      722      +30     
==========================================
+ Hits          651      675      +24     
- Misses         41       47       +6     

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