[MCA][Scheduler] Collect resource pressure and memory dependency bottlenecks.

[MCA][Scheduler] Collect resource pressure and memory dependency bottlenecks.

Every cycle, the Scheduler checks if instructions in the ReadySet can be issued
to the underlying pipelines. If an instruction cannot be issued because one or
more pipeline resources are unavailable, then field
Instruction::CriticalResourceMask is updated with the resource identifier of the
unavailable resources.

If an instruction cannot be promoted from the PendingSet to the ReadySet because
of a memory dependency, then field Instruction::CriticalMemDep is updated with
the identifier of the dependending memory instruction.

Bottleneck information is collected after every cycle for instructions that are
waiting to execute. The idea is to help identify causes of bottlenecks; this
information can be used in future to implement a bottleneck analysis.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354490 91177308-0d34-0410-b5e6-96231b3b80d8