WrapCachedDir does not work correctly with case-insensitive filesystems

[Omniflux]

WrapCachedDir does not work correctly with case-insensitive filesystems.

Should be documented or fixed...

Discovered while implementing fs.wrapcifs (Python 3.11+ only)

>>> from fs.osfs import OSFS
>>> from fs.wrap import WrapCachedDir

>>> e = OSFS('E:/')
>>> e.getmeta()['case_insensitive']
True
>>> e.isdir('Temp')
True
>>> e.isdir('temp')
True

>>> w = WrapCachedDir(e)
>>> w.getmeta()['case_insensitive']
True
>>> w.isdir('Temp')
True
>>> w.isdir('temp')
False