Expose `.url` property on store objects?

[TomNicholas]

In scenarios where you are given an ObjectStore object that you did not explicitly create, it would be nice to be able to read off the underlying store url. Mind if I add a .url property? I would add this rust-side to every store class and expose via python.

[kylebarron]

Would we be able to reliably construct a user-facing URL in all cases? Even with edge cases like S3-compliant but non-AWS stores? Would we map memory stores to memory://? I'm not sure if we have access to the canonicalized path in the LocalStore. Would that be file:///? Or could you have a file url relative to the input path?