Enables other executables to invoke dora CLI commands directly without going through the argument parsing.

Delay dropping of `DoraNode` in Python until all event data is freed

When dropping the `DoraNode`, it waits for the remaining drop tokens. This only works if all the dora events were already dropped before. With the Python GC, this is not guaranteed as some events might still be live on the heap (the user might even use them later). In such cases, we waited until we ran into a timeout, which resulted in very long exit times (see https://github.com/dora-rs/dora/issues/598).

This commit fixes this issue by adding a reference-counted copy of the `DoraNode` and `EventStream` to every event given to Python. This way, we can ensure that the underlying `DoraNode` is only dropped after the last event reference has been freed.

We need to avoid blocking the coordinator for too long.

Allows to override the log level through the `RUST_LOG` env variable.

Make `dora start` attach by default, add `--detach` to opt-out

Forwarded by coordinator

Co-authored-by: Haixuan Xavier Tao <tao.xavier@outlook.com>

Transform custom PyEvent into standard python dictionary for easier d…

Currently having a custom PyEvent make debugging very hard as fields are hidden within the class PyEvent that is defined within Rust Code.

Python user are getting really confused about this obscure class.

This PR transforms the class into a standard python dictionary.

Before this commit, there were some cases where the returned `DataflowStatus` was ignored and the reported `cascading_errors` were never applied.

The init function returns an error if another node exited before initialization. In this case, we consider the subsequent error as a cascading error and skip it when printing the error message to the user.