parseformat.Location parsing / validation

There is quite a lot of parsing and validation going on there and we also have a metric ton of tests for that.

Considering that we usually give the URL to borgstore and it is parsed and validated there again, this seems a bit much.

Maybe after #9593 is done and the old "RPC over ssh" protocol is removed and we do everything with borgstore, we could simplify this a lot and remove a lot of code.

Some stuff from Location might be also used for borg key file naming (in case of keyfile modes), so that still depends on a parsed location, see #9683.