Enable checks that require code cleanup in .clang-tidy

[alevenberg]

To enable it, remove it from the list of committed checks.

These checks are nice to have, but are current code does not conform to them. We need to cleanup the existing code first.

Checks to enable:

• [ ] bugprone-unused-return-value
• [ ] bugprone-inc-dec-in-condition
• [ ] bugprone-unused-local-non-trivial-variable
• [ ] misc-include-cleaner: too many true positives. We need to clean up the code, but we should do that over time, maybe per-directory, instead of blocking the adoption of Clang 17 until it is all fixed.