Check all devices that write files are using a compatible mount

ophyd-async devices take a DirectoryProvider, which provides two parts of the resource path: `root` and `resource_path`.
This is used by the filewriters to construct a path into the visit directory, where the data should be written and referenced externally.
The current working assumption is that all devices that make use of it will be operating as Kubernetes softIOCs, with the DLS filesystem mounted so as to expose the least access while still allowing for full functionality (i.e. for a device on beamline ixx, it should only expose `/data -> /dls/ixx/data`, preventing any data being written to the wrong beamline, while still allowing for end of year/change of visit).
Some devices may need to remain non-softIOCs, potentially mounting the whole filesystem `/dls -> /dls`.

## Acceptance Criteria
* On startup of a selected group of devices, we should be able to check that their mountpoint is mutual.

- This issue may belong in ophyd-async or blueapi?