ci: fix coverage report validation and rounding

[kralicky]

Fixes a few issues related to coverage reports:

• Use our own coverage.yaml instead of the default upstream one
• Fix coverage % rounding. The upstream behavior appears to be to round to 1 decimal place, but this is undesirable if the threshold is 100%.
• Re-enable branch coverage
• In CI, log the coverage report summary text and fail the workflow if the threshold is not reached.

[coveralls]

Coverage Report for CI Build 29787621667

Warning

No base build found for commit a949754 on main.
Coverage changes can't be calculated without a base build.
If a base build is processing, this comment will update automatically when it completes.

Coverage: 100.0%

Details

• Patch coverage: No coverable lines changed in this PR.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

Requires a base build to compare against. How to fix this →

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Coverage Stats

Relevant Lines:	7770
Covered Lines:	7770
Line Coverage:	100.0%
Relevant Branches:	4500
Covered Branches:	3434
Branch Coverage:	76.31%
Branches in Coverage %:	No
Coverage Strength:	20141.7 hits per line

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💛 - Coveralls