[MNT] Add test to check that soft dependency skipping is working as intended

[MatthewMiddlehurst]

See also #3406 #3409 #3410

Adds a test run that simply checks no tests are skipped containing the reason "soft dependency" or similar when all dependencies are installed.

Skips all actual tests after the initial pytest check for skipping.

pytest checks generated by out testing system no longer xfail (still runs but expected to fail) but skips (does not run at all). I honestly thought we were already skipping and we have never run into and unexpected pass I believe.

Only wraps tests if the pytest flag is set.

[aeon-actions-bot]

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• Run pre-commit checks for all files
• Run mypy typecheck tests
• Run all pytest tests and configurations
• Run all notebook example tests
• Run numba-disabled codecov tests
• Disable numba cache loading
• Regenerate expected results for testing
• Push an empty commit to re-run CI checks