spirv,radv,anv: implement no-op VK_GOOGLE_user_type

spirv,radv,anv: implement no-op VK_GOOGLE_user_type

This extension only allows HLSL shader compilers to optionally embed
unambiguous type information which can be safely ignored by the driver.

This fixes a crash with the recent Vulkan backend of Path Of Exile
(it uses the extension without checking if it's supported).

Cc: <mesa-stable@lists.freedesktop.org>
Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Tested-by: Edmondo Tommasina <edmondo.tommasina@gmail.com>
Reviewed-by: Jason Ekstrand <jason@jlekstrand.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/5237>