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

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dyung wrote:

> https://lab.llvm.org/buildbot/#/builders/164/builds/20521 the msan bot seems good now, but darwin still seems unhappy https://lab.llvm.org/buildbot/#/builders/23/builds/19172. I have one more PR I think could solve this, and if not, I'll have to revert the stack.

Which PR is this? I can take the bot offline and give it a try. Alternatively, is there anything I can easily do that might help to debug the issue?

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