Prepare release 8.2.1

Co-authored-by: Hynek Schlawack <hs@ox.cx>

Co-authored-by: Sam Jirovec <47160720+samjirovec@users.noreply.github.com>

Co-authored-by: Nathan Goldbaum <nathan.goldbaum@gmail.com>

…down since pytest 8.2.0

[8.2.x] unittest: fix class instances no longer released on test teardown since pytest 8.2.0

Co-authored-by: James Frost <james.frost@metoffice.gov.uk>

Co-authored-by: Bruno Oliveira <nicoddemus@gmail.com>

Co-authored-by: Florian Bruhin <me@the-compiler.org>

…ectory creation

[8.2.x] cacheprovider: fix "Directory not empty" crash from cache directory creation

…ems`

Manual minimal backport from commit e89d23b.

Fix #12355.

In the issue, it was reported that the `reorder_items` has quadratic (or
worse...) behavior with certain simple parametrizations. After some
debugging I found that the problem happens because the "Fix
items_by_argkey order" loop keeps adding the same item to the deque,
and it reaches epic sizes which causes the slowdown.

I don't claim to understand how the `reorder_items` algorithm works, but
if as far as I understand, if an item already exists in the deque, the
correct thing to do is to move it to the front. Since a deque doesn't
have such an (efficient) operation, this switches to `OrderedDict` which
can efficiently append from both sides, deduplicate and move to front.

[8.2.x] fixtures: fix catastrophic performance problem in `reorder_items`