[GreedyRA ORE] Separate Folder Reloads and Zero Cost Folder Reloads

Patchpoint instructions have operands which is actually zero cost
(or the same as register) to use the value from the stack.
In terms of statistic it makes same to separate them.

Move from computation instructions related to stack spill/reload to
number of stack slot referenced.

Reviewers: reames, MatzeB, anemet, thegameg
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D100016