[MachineScheduler] Add option to control reordering for store/load clustering (#75338)

Reordering based on the sort order of the MemOpInfo array was disabled
in <https://reviews.llvm.org/D72706>. However, it's not clear this is
desirable for al targets. It also makes it more difficult to compare the
incremental benefit of enabling load clustering in the selectiondag
scheduler as well was the machinescheduler, as the sdag scheduler does
seem to allow this reordering.

This patch adds a parameter that can control the behaviour on a
per-target basis.

Split out from #73789.