Revert "gallium/u_threaded: buffer sharedness tracking"

Revert "gallium/u_threaded: buffer sharedness tracking"

This reverts commit 8f159a8576efbb7bb3755d215a54b87c4c99a0d2.

This commit is correct but it exposes an existing bug: DISCARD_RANGE doesn't
work well with shared buffers.
So for now revert this commit as it's causing hangs on some APUs (see
https://gitlab.freedesktop.org/drm/amd/-/issues/2447) and flickering in
Metro Last Light Redux.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9108
Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/23492>