Support string methods on path objects

[AA-Turner]

cc: @stephenfin @tronical @picnixz @lucyleeow
xref: #11605

This PR would allow using str methods on paths (e.g. app.outdir.rstrip(...)). It is however very fragile.

The alternative would be to entirely revert pathlib support, but I fear downstream may have already adapted to expect usage of pathlib.Path objects.

Thoughts appreciated.

A

[picnixz]

I personally think that path objects should be used whenever possible. IIRC there has been some work in CPython to improve pathlib performances, e.g., by implementing some operations in C.

As such, it sould be better in the long term to switch now and inform users as much as possible that treating them as strings is deprecated.

Since we made the changes and some upstream repos may have already switched, it's maybe better not to revert (if we eventually plan to completely drop str aupport in some future version).

[stephenfin]

This is a total hack and I approve 👍 Let's get this out and drop it in 8.x as you suggest