[clang] [ClangRepl] Reland Semanic Code Completion (PR #75556)

[Vladimir Vereschaka via cfe-commits]

vvereschaka wrote:

I tried to revert this commit and two next ones with the warning fixes (they are related) locally on the builder. The tests have passed successfully after reverting
These commits have been reverted
* 8c296d58c50902e367f64417948d6e2d43828f36
* 8dd77fa5ae2c20cce903501e9090c663bf97d144
* 35b366ace73d0ede3cdeeb4d09150a9945750b7f

https://github.com/llvm/llvm-project/pull/75556