[clang] [analyzer][HTMLRewriter] Cache partial rewrite results. (PR #80220)

[Artem Dergachev via cfe-commits]

haoNoQ wrote:

(There isn't a lot of activity in the `HTMLRewriter` outside of myself these days but the patch is somewhat large so I decided to make a PR anyway.)

https://github.com/llvm/llvm-project/pull/80220