[clang] [clang][ssaf][NFC] Rename ssaf-linker tool to clang-ssaf-linker (PR #185631)

[Balázs Benics via cfe-commits]

steakhal wrote:

> I don't have an opinion on the name, but it'd be nice if the name of the directory (clang/tools/ssaf-linker) matched the name of the tool. If clang-ssaf-linker sticks as a name, could you rename the directory to match?

Personally, I didn't feel it's necessary because `clang` is already present in the path name - but we could come back and rename the directory sure. I'll come back to address this.

https://github.com/llvm/llvm-project/pull/185631