[ScopBuilder] Move hoistInvariantLoads to ScopBuilder. NFC.
Refactor Scop and ScopBuilder class:
1. Move hoistInvariantLoads function from Scop to ScopBuilder class.
2. Private functions (addInvariantLoads, getNonHoistableCtx) are moved
to public section of Scop class. hoistInvariantLoads function
references these functions. These functions will be moved to
ScopBuilder as well in the next steps.
Patch by Dominik Adamski <adamski.dominik@gmail.com>
Differential Revision: https://reviews.llvm.org/D62925
git-svn-id: https://llvm.org/svn/llvm-project/polly/trunk@363121 91177308-0d34-0410-b5e6-96231b3b80d8