[clang] [sanitizer] Add plumbing for -fsanitize-add-pseudo-functions and partly replace '-mllvm -array-bounds-pseudofn' (PR #138577)

[Vitaly Buka via cfe-commits]

https://github.com/vitalybuka approved this pull request.

LGTM,  but I'd prefer shorted name, e.g. 
We have `-fsanitize-trap`, `-fsanitize-report-with-trap`

so `-add-` is unnecessary
plural functions as well
maybe pseudofn is good enough



https://github.com/llvm/llvm-project/pull/138577