Deprecate `prepare_data_per_node` and auto detect shared file-system

Nobody has claimed this yet.

## Proposed refactor

This was proposed by @tchaton on live-stream. `prepare_data_per_node`can be identified by dumping a file on rank 0 and checking whether all other ranks can see that file or not. In the case of a multi-node system, if the file system is shared then all of them will be able to see that file, else not.

### Motivation

This way users won't have to take care of setting this flag manually.

### Pitch

possible pseudocode (feel free to update this or comment)
```py
if global_rank == 0:
filename = 'something_{uuid()}.txt'
broadcast(filename)
dump_file(filename)

barrier()

if global_rank == 0
is_file_present = does_file_exist(filename)
is_file_present = all_gather(is_file_present)
prepare_data_per_node = is_file_present.all()
prepare_data_per_node = broadcast(prepare_data_per_node)
```

any other alternatives??

### Additional context

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cc @borda @justusschock @kaushikb11 @awaelchli @ananthsub @ninginthecloud @jjenniferdai @rohitgr7 @akihironitta

Start by locating the prepare_data_per_node option and the distributed data-preparation entry points. Review the proposed rank, barrier, file-visibility, and broadcast flow, along with existing distributed tests if available. Done means the flag's deprecation and automatic shared-filesystem detection have agreed behavior and coverage across shared and non-shared filesystems.

Written by the indexing model from the issue text.