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

[Vassil Vassilev via cfe-commits]

vgvassilev wrote:

@gribozavr, after this PR we will need to have `dot` for the sphinx documentation for the bots. Could you install it on the bots? Eg, https://lab.llvm.org/buildbot/#/builders/92/builds/49520

Further details: https://discourse.llvm.org/t/any-tool-for-creating-editable-diagrams-in-llvm-clang-repl-documentation-similar-to-mermaid-ingithub/72729/2

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