[clang] [clang] Do not compute typo-correction suggestions for disabled diagnostics (PR #209694)

[Erich Keane via cfe-commits]

https://github.com/erichkeane commented:

There are some other general improvements here, but can we get the performance tool to take a look at this?  This pessimizes the 'common' case, so I'd like to make sure we're not paying a high cost for some slight improvement for the rest.

https://github.com/llvm/llvm-project/pull/209694