ENH: Better event count rep and noise_cov_method

[larsoner]

Before merging …

• [x] Changelog has been updated (docs/source/changes.md)

Closes #846

Alongside https://github.com/mne-tools/mne-bids/pull/1227 and https://github.com/mne-tools/mne-python/pull/12447 produces for example:

main	PR

It's more impressive on other examples but you can at least see that it turns it into a datatable and also fixes the overflow.

Also:

• Snuck in a noise_cov_method = "shrunk" option, too. It's useful when debugging to set this to empirical for example for speed.
• Added a --pdb alias for --debug to mirror the pytest option by the same name (I mistakenly use --pdb a lot and I don't think there's any issue with having an alias)

[hoechenberger]

Thank you, very nice indeed