Split hgq tests and isolate qkeras tests to make tests run in under 1h

[JanFSchulte]

Attempt to reconfigure pytests so that they reliably finish in under 1h and don't get killed.

The HGQ tests are split into two and both are run standalone. The QKeras test is also added to the list of long-running tests that should not be run in the same batch as other tests.

Type of change

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Tests

No new tests, but hopefully existing ones will pass.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.

[JanFSchulte]

pre-commit.ci autofix

[jmitrevs]

Do we need to split even more tests?

[jmitrevs]

Or only merge 3 tests?