finally suites in try/except blocks have very complex control flow, which we don't yet model, and need to.

I've already written extensively about the complexities of finally blocks, so I won't try to summarise them again here. Instead, I'll point to:

• This TODO comment here: https://github.com/astral-sh/ruff/blob/76e4277696e8b34b771d554f8f0d07054d413289/crates/red_knot_python_semantic/src/semantic_index/builder.rs#L929-L939
• The various finally-related TODO comments in our exception-handler control-flow test suite, from this point onwards: https://github.com/astral-sh/ruff/blob/main/crates/red_knot_python_semantic/resources/mdtest/exception/control_flow.md#exception-handlers-with-finally-branches-but-no-except-branches
• The full writeup of exception-handler control flow I put together here: https://astral-sh.notion.site/Exception-handler-control-flow-11348797e1ca80bb8ce1e9aedbbe439d