[clang] [llvm] [KCFI][NFC] Rename the !kcfi_type Function metadata to !cfi_type (PR #109080)

[Fangrui Song via cfe-commits]

MaskRay wrote:

I understand the intention to generalize naming, but I feel that there is significance chance that the over-generalization may not work with the alternative CFI schemes, and this change could turn out to be needed when the other schemes go with different IR constructs.

I feel that we should make such renaming at this time.

BTW: when kcfi was proposed, I felt that it was not a good name because the strategy could only cover a very limited subset of LTO-based `-fsanitize=cfi`. kcfi is just like a brand name.

https://github.com/llvm/llvm-project/pull/109080