[clangd] Add a flag to clangdServer rename function to control whether we want format the replacements.
This would allow clangd embedders to use the ClangdServer::rename for other
purposes (highlighting all the occurrences of the symbol in prepare
Reviewers: sammccall, ilya-biryukov
Subscribers: MaskRay, jkorous, arphaman, kadircet, cfe-commits
Differential Revision: https://reviews.llvm.org/D64481