Add 'sync' command to Python client

[cottsay]

The Python method encompasses both the SYNC and SYNC_PATTERN Assuan commands, choosing the correct one depending on whether a pattern was given.

This includes some mild refactoring:

• in client.c to de-duplicate the arch_list parsing.
• in test_smoke.py to better support the new functionality.

[cottsay]

Looks like the test fixture repositories checked into this repo use zstd compression, which isn't supported by the version of createrepo-c in Ubuntu. I'll need to re-generate them with a compatible compression algorithm and re-sign the metadata.

Back to draft until that has been resolved.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 83.33333% with 6 lines in your changes missing coverage. Please review.
✅ Project coverage is 48.86%. Comparing base (44c151f) to head (e90668a).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/python/client.c	83.33%	3 Missing and 3 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #29      +/-   ##
==========================================
+ Coverage   42.67%   48.86%   +6.18%     
==========================================
  Files          20       20              
  Lines        2615     2642      +27     
  Branches      532      538       +6     
==========================================
+ Hits         1116     1291     +175     
+ Misses       1244     1046     -198     
- Partials      255      305      +50     

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[cottsay]

Alright, this can be reviewed now, but I'm keeping it in draft until #30 has been merged.