feat: add comprehensive type annotations

[huynguyengl99]

Close #647

[huynguyengl99]

Hi @bckohan and @JohananOppongAmoateng, this PR is based on the type annotations I added in the typeshed repo. Could you take a look at it? Also, if everything looks good, could you approve the GitHub workflows to run, @bckohan?

[huynguyengl99]

Hi @bckohan, could you re-approve the workflow run? I’ve updated the tests, so I expect it should pass now.

There are still quite a few typing errors, but I think we can address them in future commits in this PR—either when I have more time, or with the help of @JohananOppongAmoateng.

[codecov]

Codecov Report

❌ Patch coverage is 98.41270% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.33%. Comparing base (2468a08) to head (95f84a6).

Files with missing lines	Patch %	Lines
src/polymorphic/query.py	92.42%	1 Missing and 4 partials ⚠️
src/polymorphic/utils.py	96.29%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #856      +/-   ##
==========================================
+ Coverage   90.95%   91.33%   +0.37%     
==========================================
  Files          28       28              
  Lines        1725     1835     +110     
  Branches      268      273       +5     
==========================================
+ Hits         1569     1676     +107     
- Misses        104      105       +1     
- Partials       52       54       +2     

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