[clang] [clang-tools-extra] Remove `StringLiteral` in favor of `StringRef` (PR #122366)

[Nikita Popov via cfe-commits]

nikic wrote:

I didn't really understand the last paragraph of the PR description. How does using StringRef instead of StringLiteral reduce relocations?

https://github.com/llvm/llvm-project/pull/122366