[InlineCost] InlineCostAnnotationWriterPass introduced

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

Reviewers: apilipenko, mtrofin, davidxl, fedor.sergeev

Reviewed By: mtrofin

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