This class allows to see the inliner's decisions for better
optimization verifications and tests. To use, use flag
"-passes="print<inline-cost>"".

This is the second attempt to integrate the patch.
The problem from the first try has been discussed and
fixed in D82205.

Reviewers: apilipenko, mtrofin, davidxl, fedor.sergeev

Reviewed By: mtrofin

Differential revision: https://reviews.llvm.org/D81743