Improve handling of versions

[cthoyt]

This was motivated by #21, where it was annoying to do str(version) when looping through versions. Now, functions in chembl-downloader will also accept integer versions.

This also makes some more careful testing of the way that versions are normalized, especially for versions before v10 and the two instances of versions that have a minor (i.e., v22.1 and v24.1)

This allows:

import chembl_downloader

for version in range(30, 36):
    count = chembl_downloader.query_scalar(
        'SELECT COUNT(activity_id) FROM activities', 
        version=version,
    )

[codecov]

Codecov Report

❌ Patch coverage is 91.30435% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.30%. Comparing base (80c7afc) to head (cdebcde).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/chembl_downloader/api.py	91.30%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #22      +/-   ##
==========================================
+ Coverage   41.21%   48.30%   +7.09%     
==========================================
  Files           4        4              
  Lines         330      354      +24     
  Branches       55       56       +1     
==========================================
+ Hits          136      171      +35     
+ Misses        164      157       -7     
+ Partials       30       26       -4     

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