[PGO] Extend the value profile buckets for mem op sizes.

[PGO] Extend the value profile buckets for mem op sizes.

Extend the memop value profile buckets to be more flexible (could accommodate a
mix of individual values and ranges) and to cover more value ranges (from 11 to
22 buckets).

Disabled behind a flag (to be enabled separately) and the existing code to be
removed later.

Differential Revision: https://reviews.llvm.org/D81682