ci: improve jobs

[caarlos0]

• enable lfs on checkout
• merge build and coverage, as they both do pretty much the same thing

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 36.95%. Comparing base (e9cb9d2) to head (b8b64b9).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #662      +/-   ##
==========================================
+ Coverage   36.64%   36.95%   +0.31%     
==========================================
  Files         187      188       +1     
  Lines       16512    16695     +183     
==========================================
+ Hits         6050     6169     +119     
- Misses      10089    10145      +56     
- Partials      373      381       +8     

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