glamor: Use GBM for BO allocation when possible

Inspired by amdgpu. This avoids various issues due to a GEM handle
lifetime conflict between us and Mesa with current glamor.

Bugzilla: https://bugs.freedesktop.org/105381


Tested-by: Konstantin Kharlamov <hi-angel@yandex.ru>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>