[Power10] Enable the heuristic for Power10 and switch the sched model

with P9 Model

Enable the pre-ra and post-ra scheduler strategy for Power10 as we want
to customize the heuristic later. And switch the scheduler model with P9
model before P10 Model is available. The NoSchedModel is modelled as
in-order cpu and the pre-ra scheduler is not bi-directional which will
have big impact on the scheduler.

Reviewed By: jji

Differential Revision: https://reviews.llvm.org/D86865