[NewPassManager] Add tuning option: ForgetAllSCEVInLoopUnroll [NFC].

Summary: Mirror tuning option from old pass manager in new pass manager.

Reviewers: chandlerc

Subscribers: mehdi_amini, jlebar, zzheng, dmgreen, llvm-commits

Tags: #llvm

Differential Revision: https://reviews.llvm.org/D61612

llvm-svn: 361560