[clang/LLVM] Add flatten_deep attribute for depth-limited inlining (1/2)#165777

grigorypas wants to merge 4 commits intollvm:mainllvm/llvm-project:mainfrom

grigorypas:add_flatten_deep_to_clanggrigorypas/llvm-project:add_flatten_deep_to_clangCopy head branch name to clipboard