Provide annotations for `kombu/utils/encoding.py`

[Harry-Lees]

Linked Issue: #1511

For this PR, I aimed to annotate the existing implementation of the encoding functions, regardless of what I thought the function's intention is.

There are some functions e.g. str_to_bytes, bytes_to_str, or safe_str which I think may have potentially misleading implementations. I'm not sure whether this is under the scope of this PR, input on this would be appreciated :).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 81.81818% with 4 lines in your changes missing coverage. Please review.

Project coverage is 81.52%. Comparing base (1001431) to head (7c3e8fc).

Files with missing lines	Patch %	Lines
kombu/utils/encoding.py	81.81%	0 Missing and 4 partials :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2208      +/-   ##
==========================================
- Coverage   81.54%   81.52%   -0.03%     
==========================================
  Files          77       77              
  Lines        9517     9527      +10     
  Branches     1154     1158       +4     
==========================================
+ Hits         7761     7767       +6     
  Misses       1564     1564              
- Partials      192      196       +4     

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[Harry-Lees]

My thoughts on this type of type only changes. I think we should discourage this type of contributions. Instead we should allow / encourage this type of changes only in real bugfix /feature adding pr

Is there anything that should be done to get this PR mergable? I'm happy to close this if the project is no-longer accepting typing-only PRs, otherwise I think I have addressed the comments on the PR.