[clangd] Provide patched diagnostics with preamble patch

[clangd] Provide patched diagnostics with preamble patch

Translates diagnostics from baseline preamble to relevant modified
contents.

Translation is done by looking for a set of lines that have the same
contents in diagnostic/note/fix ranges inside baseline and modified
contents.

A diagnostic is preserved if its main range is outside of main file or
there's a translation from baseline to modified contents. Later on fixes
and notes attached to that diagnostic with relevant ranges are also
translated and preserved.

Depends on D143095

Differential Revision: https://reviews.llvm.org/D143096