[clang] [llvm] [clang][Inliner] Add opt-in inliner hints for lambdas and implementation-file functions (PR #228074)

[Eli Friedman via llvm-commits]

efriedma-quic wrote:

I think we need to come up with names that actually describe the relevant properties, so it's clear what the contract is.

If I'm understanding correctly, the interesting property of lambdas, specifically, is that they only have one "use": the caller function.  clang-main-file sounds like it's basically "make heuristics assume we don't actually have any other definitions of this function for even though it's technically required to be weak".

https://github.com/llvm/llvm-project/pull/228074