Fix several CI issues

[gwynne]

• Update the list of versions for Swift images
• Update actions/checkout to v5
• Disable TSan when building with Swift 5.10 and 6.0 due to swift-crypto hitting a compiler crasher
• Add macOS Sequoia tests
• Remove Homebrew bug workaround (no longer needed)
• Add installing curl to the Linux unit tests for Codecov
• Fix the long-broken (but with the failure hidden by TSan) testReserveCapacityIsForwarded test.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.45%. Comparing base (ecbc3eb) to head (b2477c4).
⚠️ Report is 18 commits behind head on main.

Additional details and impacted files

@@ Coverage Diff @@ ## main #579 +/- ## ========================================== + Coverage 62.16% 62.45% +0.28%  ========================================== Files 130 132 +2 Lines 10422 10472 +50 ========================================== + Hits 6479 6540 +61  + Misses 3943 3932 -11 

see 5 files with indirect coverage changes

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[fabianfett]

Love it!