[GreedyRA ORE] Compute ORE stats if extra analysis is enabled

To save compile time, avoid computation of stats if ORE will not emit it.
The motivation is to add more stats and compute it only if it will dumped.

Reviewers: reames, MatzeB, anemet, thegameg
Reviewed By: reames
Subscribers: llvm-commits
Differential Revision: https://reviews.llvm.org/D100010