[Inline][Remark][NFC] Optionally provide inline context to inline

advisor.

This patch has no functional change, and merely a preparation patch for
main functional change. The motivating use case is to annotate inline
remark pass name with context information (e.g. prelink or postlink,
CGSCC or always-inliner), see D125495 for more details.

Differential Revision: https://reviews.llvm.org/D126824