Check floats according to 2025-09

[mzuenni]

The 2025-09 spec defines what a floating point is. This PR changes the default_compare.cc accordingly.

[meisterT]

@mzuenni I have just created some basic tests in #3183 - I think it makes sense to merge that one first and then add more tests that do not pass today but pass after your changes.

Also consider splitting up the formatting-only changes into a separate commit

[mzuenni]

@meisterT sounds good. Some inspiration for tests: https://github.com/RagnarGrootKoerkamp/BAPCtools/blob/main/test/default_output_validator/default_output_validator.yaml (with these changes all those tests should be passed)