apt: add apt pinning support

[lengau]

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CRAFT-1645

[codecov[bot]]

Codecov Report

Merging #40 (9a27b17) into main (e49a3d9) will increase coverage by 0.24%. The diff coverage is 84.44%.

:exclamation: Current head 9a27b17 differs from pull request most recent head 937872f. Consider uploading reports for the commit 937872f to get more accurate results

@@            Coverage Diff             @@
##             main      #40      +/-   ##
==========================================
+ Coverage   81.92%   82.17%   +0.24%     
==========================================
  Files          11       12       +1     
  Lines         520      645     +125     
  Branches      114      143      +29     
==========================================
+ Hits          426      530     +104     
- Misses         72       85      +13     
- Partials       22       30       +8     

Impacted Files	Coverage Δ
craft_archives/repo/installer.py	50.00% <20.00%> (-4.84%)	:arrow_down:
craft_archives/repo/package_repository.py	81.12% <78.84%> (-1.89%)	:arrow_down:
craft_archives/repo/apt_preferences_manager.py	91.89% <91.89%> (ø)
craft_archives/repo/errors.py	82.35% <100.00%> (+1.70%)	:arrow_up:

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