[clang] Add Documentation for Execution Results Handling in Clang-Repl (PR #65650)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> @AaronBallman, we need to install dot/doxygen on this machine as Sphinx requires graphviz. The PR has a link to the discussion and we could not find the bot owners.

Ouch, we've struggled recently to get the attention of the sphinx bot owners. :-(

The publication bot is still working: https://lab.llvm.org/buildbot/#/builders/89/builds/49495 and seems to be generating the docs for clang-tools-extra:
```
42.046 [42/24/363] Generating html Sphinx documentation for clang-tools into "/home/buildbot/as-worker-4/publish-sphinx-docs/build/tools/clang/tools/extra/docs/html"
```
so I don't think we need to revert the changes here (the Clang and LLVM sphinx bots are also broken because we needed the machine to be modified by the bot owners, so there is already precedence). However, you should be aware that the sphinx publish bot does not send out email notifications when the documentation is broken -- you need to manually keep track of the state of things. We're trying to improve this situation, so I don't expect that to be a forever problem, but it's something to keep in mind. CC @LegalizeAdulthood @carlosgalvezp @njames93 for awareness as other frequent reviewers of clang-tools-extra stuff.

https://github.com/llvm/llvm-project/pull/65650