Migrate codecov to GitHub Action

[kwridan]

Describe your changes

• The codecov bash uploader is deprecated and will no longer work starting February 2022
• The recommendation is to migrate to an alternate uploader, in our case v2 of the GitHub codecov action

Test Plan

• Ran make test_ci
• Verify coverage reports are still saved to the .coverage directory

Additional context

References:

• https://docs.codecov.com/docs/about-the-codecov-bash-uploader

[codecov]

Codecov Report

Merging #101 (3fef652) into main (a314558) will increase coverage by 0.11%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##             main     #101      +/-   ##
==========================================
+ Coverage   96.22%   96.33%   +0.11%     
==========================================
  Files          47       47              
  Lines        1853     2400     +547     
==========================================
+ Hits         1783     2312     +529     
- Misses         70       88      +18     

Impacted Files	Coverage Δ
Sources/XCDiffCore/Library/XcodeProjLoader.swift	66.66% <0.00%> (-19.05%)	⬇️
Sources/XCDiffCore/ProjectComparator.swift	97.72% <0.00%> (-2.28%)	⬇️
...ffCore/Comparator/ResolvedSettingsComparator.swift	98.75% <0.00%> (-1.25%)	⬇️
Sources/XCDiffCore/Library/SettingsHelper.swift	94.33% <0.00%> (-0.54%)	⬇️
Sources/XCDiff/main.swift	0.00% <0.00%> (ø)
Sources/XCDiffCommand/Utils.swift	0.00% <0.00%> (ø)
Sources/XCDiffCore/Library/Diff.swift	100.00% <0.00%> (ø)
Sources/XCDiffCore/ComparatorType.swift	100.00% <0.00%> (ø)
Sources/XCDiffCore/Library/System.swift	0.00% <0.00%> (ø)
Sources/XCDiffCore/Library/PathHelper.swift	100.00% <0.00%> (ø)
... and 37 more

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