Schedule Hot Cold Splitting pass after most optimization passes

Summary:
In the new+old pass manager, hot cold splitting was schedule too early.
Thanks to Vedant for pointing this out.

Reviewers: sebpop, vsk

Reviewed By: sebpop, vsk

Subscribers: mehdi_amini, llvm-commits

Differential Revision: https://reviews.llvm.org/D53437

llvm-svn: 344869