[clang-tools-extra] Reapply "[clang-doc] Move Info types into arenas (#190054)" (PR #192495)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> > Thanks. I guess I need to figure out why its passing on our bot, but failing on yours.
> 
> I can try updating the version of clang on the machine over the weekend to see if it makes a difference if this is not terribly urgent to get in.

It can wait. I'd prefer to get it relanded sooner rather than later, since it complicates other work in clang-doc, but its not critical for anything ATM. I did update the patch slightly to see if there is some difference due to the use of a copy over a move when putting things into the arena. I'm not super confident that this will make any difference, but this seems like its a very subtle issue that's causing things to go awry.

The other things that I know are different on our CI bots:

1. We use a very recent clang (within a week usually or from the same build in many cases).
2. We use the in-tree libc++.
3. We use lld over ld64.

other than those specific bits, things are largely the same from what I can tell.

https://github.com/llvm/llvm-project/pull/192495