mesa: add _mesa_HashFindFreeKeys

_mesa_HashFindFreeKeyBlock function returns a name range, so it cannot be
used to recycle non-consecutive names.

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/6600>
2 files changed