[INFRA] CI and Compilers

[eseiler]

• Uses docker images from seqan/actions
• Removes CMake 3.5 test (prone to errors with newer operating systems, and hard to get running)
• gcc-14 support
• clang-18 support
• Change default of SEQAN3_VERBOSE_TESTS to OFF. ON is a bad default because we basically always set it to OFF explicitly
• Simplify coverage generation. I don't think we ever use it to build local HTML reports. And not doing everything in CMake makes it much easier to maintain (and read).

I did not yet update the cron jobs (follow-up).

[vercel[bot]]

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Name	Status	Preview	Updated (UTC)
seqan3	✅ Ready (Inspect)	Visit Preview	Jul 18, 2024 3:52pm

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 98.12%. Comparing base (69284e8) to head (a151471).

:exclamation: Current head a151471 differs from pull request most recent head 82e9727

Please upload reports for the commit 82e9727 to get more accurate results.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #3270 +/- ## ========================================== - Coverage 98.18% 98.12% -0.07% ========================================== Files 270 270 Lines 11885 11921 +36 Branches 0 105 +105 ========================================== + Hits 11669 11697 +28 - Misses 216 224 +8 ```

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