Add Cam FM catch up extractors

[garret1317]

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Description of your pull request and other information

This PR adds support for Cam FM, Cambridge and Anglia Ruskin University's student radio station.

• Wikipedia article
• About page

It doesn't support the live stream. Generic extractor works alright enough™ (plays in mpv), and there's not really anything to extract anyway

I added a new date format in utils.py to make unified_timestamp work.

Template

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• Fix or improvement to an extractor (Make sure to add/update tests)
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[garret1317]

per #7083 (comment), have refined the regexes by mostly replacing them with get_element(s)_by_class