panfrost: Prepare things for v10/CSF support
What does this MR do and why?
Collection changes that will simplify addition of v10/CSF support.
There's no fundamental changes here, we basically just move code around to make things less messy when we get to introduce v10/CSF changes.
The idea is to keep all files in src/gallium/drivers/ job-frontend agnostic, and have pan_{jm,csf}.{c,h} files that take care of the JM/CSF specific bits (job descriptor emission/linking for JM, command stream building for CSF). Given most descriptors are still common to JM/CSF, we keep pan_cmdstream.c and introduce pan_cmdstream.h so we can share some useful helpers.
This series is based on !26221 (merged).
/cc @kusma