[clang] [clang-tools-extra] [clangd] Add InsertReplaceEdit for code completion (PR #187623)

[via cfe-commits]

timon-ul wrote:

> Basically, the client has to indicate support for InsertReplaceEdit in the client capabilities (done via the insertReplaceSupport flag), and the server should only send an InsertReplacedEdit in CompletionItem.textEdit for clients that indicated this support; for other clients, it should continue sending a TextEdit.

Yeah thinking about this again this makes sense and the current implementation at least seems to honor this, the problem is that as I mentioned for me it broke when I just switched my clangd to the one from this PR (without enabling replace support), which shouldn't be the case. @argothiel did u test this on your machine?

https://github.com/llvm/llvm-project/pull/187623