When tracking defs in finalizeBundle two sets are used. LocalDefs is
used to track defined virtual and physical registers, while LocalDefsP
is used to track defined register units for the physical registers.

This patch moves the updates of LocalDefsP to only iterate over regunits
when a new physical register is added to LocalDefs. When the physical
register already is present in LocalDefs, then the corresponding
register units are present in LocalDefsP. So it was a waste of time to
add them to the set again.

Cause:
1. `implicit_def` inside bundle does not count for define of reg in
machineinst verifier
2. Including `implicit_def` will cause relative reg not define, result
in `Bad machine code: Using an undefined physical register` in the
machineinst verifier

Fixes https://github.com/llvm/llvm-project/issues/139102

---------

Co-authored-by: Matt Arsenault <Matthew.Arsenault@amd.com>

Replace its only use in the AMDGPU R600 backend with a call to
finalizeBundles.

This allows for unit testing of finalizeBundle with standard MIR tests
using update_mir_test_checks.py.

Use all_uses and all_defs instead of separate Defs vector. Use
SmallSetVector instead of separate SmallSet and SmallVector. Remove
unneeded `Added` set. Fold FrameSetup/FrameDestroy into the main loop
instead of doing a separate loop over the bundled instructions.

This was looking for full copies produced by SplitKit, but SplitKit
introduces copy bundles if not all lanes are live. The scan for uses
needs to look at bundles, not individual instructions.

This is a prerequisite to avoiding some redundant spills due to
subregisters which will help avoid an allocation failure in a future
patch.

Differential Revision: https://reviews.llvm.org/D148613