radv: set radv_zero_vram=true for Unreal Engine 4/5

radv: set radv_zero_vram=true for Unreal Engine 4/5

Unreal Engine seems to rely on uninitialized memory and
RADV_DEBUG=zerovram fixes a bunch of issues.

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9025
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9380
Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/9026
Cc: mesa-stable
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/26188>
(cherry picked from commit bb92c34c2859c2f5b42c9b6ba4f5603d79b72d33)