[clang] [clang][analyzer][doc] Migrate ClangSA www FAQ section (PR #112831)

[Donát Nagy via cfe-commits]

https://github.com/NagyDonat commented:

Overall LGTM, with some minor bikeshedding on the redirect page.

I also added several inline comments about the _content_ of the page, but the content changes should be left for a separate follow-up commit to separate migrating the text and changing it.

https://github.com/llvm/llvm-project/pull/112831