panfrost: Fix reference counting with batch->resources

panfrost: Fix reference counting with batch->resources

Refactor accesses to batch->resources to happen through safe helpers
that update the appropriate bookkeeping. This makes it obvious that (in
particular) reference counts are updated when they should be.

The functional change is that we are now correctly unreferencing
resources during shadowing, fixing a leak of shadowed resources.

Closes: #7362
Fixes: 2d8f28df731 ("panfrost: Replace resource shadowing flush")
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Reported-by: Mastodon, apparently
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19753>