panfrost/midgard: Refactor schedule/emit pipeline

panfrost/midgard: Refactor schedule/emit pipeline

First, this moves the scheduler and emitter out of midgard_compile.c
into their own dedicated files.

More interestingly, this slims down midgard_bundle to be essentially an
array of _pointers_ to midgard_instructions (plus some bundling
metadata), rather than the instructions and packing themselves. The
difference is critical, as it means that (within reason, i.e. as long as
it doesn't affect the schedule) midgard_instrucitons can now be modified
_after_ scheduling while having changes updated in the final binary.

On a more philosophical level, this removes an IR. Previously, the IR
before scheduling (MIR) was separate from the IR after scheduling
(post-schedule MIR), requiring a separate set of utilities to traverse,
using different idioms. There was no good reason for this, and it
restricts our flexibility with the RA. So unify all the things!

Signed-off-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Reviewed-by: Ryan Houdek <Sonicadvance1@gmail.com>