broadcom/simulator: enable multisync in the simulator

broadcom/simulator: enable multisync in the simulator

Use drmSyncobjSignal to signal out_syncobjs when a GPU job submission
ends in the simulator. With this, we can enable multisync support in the
simulator and keep the multisync approach to process fence by submitting
a serialized no-op job that adds the fence to the array of out syncobjs,
i.e.  syncobjs to be signaled in the kernel when a job completes (job
post deps).

Signed-off-by: Melissa Wen <mwen@igalia.com>
Reviewed-by: Iago Toral Quiroga <itoral@igalia.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/14768>