Migrate PGOMemOptSizeOpt to use new OptimizationRemarkEmitter Pass

Summary:
Fixes PR33790.

This patch still needs a yaml-style test, which I shall write tomorrow

Reviewers: anemet

Reviewed By: anemet

Subscribers: anemet, llvm-commits

Differential Revision: https://reviews.llvm.org/D35981

llvm-svn: 309497