FormulaURILoader: use regex to validate refs before attempting to cast

[Rylan12]

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Fixes #17752

This PR updates Formulary::FromURILoader to match the cask equivalent and check the ref against a URI regex. This avoids trying to run URI() where the argument is something that will throw a bad URI error (e.g. a string with spaces).

[apainintheneck]

This approach makes sense to me. It might even be simpler to just catch the URI error in the .try_new method assuming there isn't a noticeable performance difference. Then you'd be able to avoid the regex caching.

[Rylan12]

This approach makes sense to me. It might even be simpler to just catch the URI error in the .try_new method assuming there isn't a noticeable performance difference. Then you'd be able to avoid the regex caching.

Sorry, I missed this comment before. I'm not opposed to doing it this way, but the regex is provided by URI seemingly for this purpose so in some ways this seems like the intended way to do it. But no really preference either way