drm/tests: connector: Add tests for drmm_connector_init

drmm_connector_init is the preferred function to initialize a
drm_connector structure. Let's add a bunch of unit tests for it.

Reviewed-by: Maíra Canal <mcanal@igalia.com>
Signed-off-by: Maxime Ripard <mripard@kernel.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20240222-kms-hdmi-connector-state-v7-5-8f4af575fce2@kernel.org