[TLI] Per-function fveclib for math library used for vectorization

Summary:
Encode `-fveclib` setting as per-function attribute so it can threaded through to LTO backends. Accordingly per-function TLI now reads
the attributes and select available vector function list based on that. Now we also populate function list for all supported vector
libraries for the shared per-module `TargetLibraryInfoImpl`, so each function can select its available vector list independently but without
duplicating the vector function lists. Inlining between incompatbile vectlib attributed is also prohibited now.

Subscribers: hiraditya, dexonsmith, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77632