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

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

This appears to have broken the clang-tools-extra Sphinx bot: https://lab.llvm.org/buildbot/#/builders/115/builds/54901

```
CMake Error at /home/buildbot/llvm-build-dir/clang-tools-sphinx-docs/llvm/src/clang/docs/CMakeLists.txt:110 (message):
  Cannot find DOT
```


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