backends/drm: Use drmModeGetConnectorTypeName()
It ensures that connector type naming is consistent across compositors and saves us some work adding string mappings.
drmModeGetConnectorTypeName() uses the same naming scheme as the drm backend so the client side should be unaffected by this change.
Upstream MR - https://gitlab.freedesktop.org/mesa/drm/-/merge_requests/222
Edited by Vlad Zahorodnii