[clang-tools-extra] [clang-doc] Move Info types into arenas (PR #190054)

[Paul Kirth via cfe-commits]

ilovepi wrote:

I did update: https://github.com/llvm/llvm-project/pull/191644 with what I hope was the missing functionality. If not ... I'm really lost. 

https://github.com/llvm/llvm-project/pull/190054