[clang] [ClangFormat] Add DiagHandler for getStyle function (PR #91317)

[Björn Schäpers via cfe-commits]

HazardyKnusperkeks wrote:

For the record, I see no harm in this PR and would also merge it without an issue. Just giving @mydeveloperday a bit more time to answer. :)

https://github.com/llvm/llvm-project/pull/91317