Revert "Revert "[llvm][NFC] Cleanup uses of std::function in Inlining-related APIs""

This reverts commit 454de99a.

The problem was that one of the ctor arguments of CallAnalyzer was left
to be const std::function<>&. A function_ref was passed for it, and then
the ctor stored the value in a function_ref field. So a std::function<>
would be created as a temporary, and not survive past the ctor
invocation, while the field would.

Tested locally by following https://github.com/google/sanitizers/wiki/SanitizerBotReproduceBuild

Original Differential Revision: https://reviews.llvm.org/D79917