Draft: Don't crash on symlinks that point outside asset_io.root_path.

[golddranks]

Objective

• Some exploration with possible solutions to Filesystem watching crashes with symlinks pointing outside the asset folder #5689

Solution

• Using the pathdiff crate (which apparently is foraged from the Rust stdlib relpath calculating implementation, but never stabilized and was replaced with simpler strip_prefix!), we can prevent Bevy from panicking and crashing, but this isn't an ideal solution, as it still doesn't understand that the assets loaded from outside the asset directory path are the same as the ones inside, so the filesystem watching functionality doesn't update the right asset. For assets that are originally meant to be picked up dynamically via filesystem watching events, it somehow works, but this is almost never the case.

[bas-ie]

Backlog cleanup: lack of activity. In other PRs, symlinks have been discussed and the general sense seems to be that we should avoid symlinks rather than cater for them.