Make delimiter in rich progress bar configurable

[quintenroets]

What does this PR do?

Fixes #18366

Enables configurable delimiter in the metrics display column of the rich progress bar

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[awaelchli]

LGTM. Could you also add a changelog entry? (in src/lightning/pytorch/CHANGELOG.md)

[quintenroets]

LGTM. Could you also add a changelog entry? (in src/lightning/pytorch/CHANGELOG.md)

Should I make a new PR for this?

[awaelchli]

No worries, this isn't a critical thing. We will include the update in one of the next PRs.

Thanks a lot for your contributions.

[quintenroets]

No worries, this isn't a critical thing. We will include the update in one of the next PRs.

Thanks a lot for your contributions.

Okay, perfect! Thank you for helping me and giving me the opportunity to contribute.