[clang] [clang-tools-extra] [llvm] [libcxx] [libcxx] adds ranges::fold_left_with_iter and ranges::fold_left (PR #75259)

[Konstantin Varlamov via cfe-commits]

https://github.com/var-const commented:

This patch has changed substantially since I last reviewed it. I'll send more feedback in a follow-up review.

https://github.com/llvm/llvm-project/pull/75259