[NFC intended] Refactor SinkAndHoistLICMFlags to allow others to construct without exposing internals
Refactor SinkAdHoistLICMFlags from a struct to a class with accessors and constructors to allow other
classes to construct flags with meaningful defaults while not exposing LICM internal details.
Author: Jamie Schmeiser <firstname.lastname@example.org>
Reviewed By: asbirlea (Alina Sbirlea)
Differential Revision: https://reviews.llvm.org/D90482