[clang-tools-extra] [include cleaner] Use tooling::HeaderIncludes for include insertions and deletions (PR #212852)

[via cfe-commits]

dmaclach wrote:

#213751 has landed (which is the reason for making this change). With #213751 adding an include and an import to the same path will dedupe and give you just the import.

(also the new way is less magic!)

https://github.com/llvm/llvm-project/pull/212852