[PGO][PGSO] Add an optional query type parameter to shouldOptimizeForSize.

Summary:
In case of a need to distinguish different query sites for gradual commit or
debugging of PGSO. NFC.

Reviewers: davidxl

Subscribers: hiraditya, zzheng, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D70510