Jungfrau: Decide on path provider logic

[olliesilvester]

During Jungfrau testing we've tried a few different things for setting the path, all of which were quite fiddly. It's a bit to sort this out properly at the moment since the way we actually launch Bluesky is also in flux. Until we're using BlueAPI properly, we should commit something which gives us something sensible in the meantime. I think good behaviour is:

• Storage directory from the parameters is taken as the file path for the Jungfrau. Pathprovider then auto increments in a nicer way than AutoIncrementingPathProvider (i.e it doesn't go back to 0 once you restart python)
• Filename is worked out based off plan metadata
• Error if file with this name already exists in this path (shouldn't happen if the provider is made properly)
• Remove override_file_path from the existing plans

Acceptance Criteria

• Path logic implemented which matches above behaviour

[olliesilvester]

We can probably just use the provider Nick made on the working branch, it worked quite well: https://github.com/bluesky/ophyd-async/blob/a7bb3dcf28a4c06f895f2547ac6b59aa8307564f/src/ophyd_async/core/_providers.py#L78

[olliesilvester]

We're going to use bluesky/ophyd-async#1147 to increment directories, and numtracker to give us the path up to the visit.