This way we get an error on incompatible types, instead of sending out invalid data.

Small refactoring

It's now bundled with the main dora library, so there's no need to release it separately.

git-subtree-dir: libraries/extensions/ros2-bridge
git-subtree-mainline: 8e7688a593
git-subtree-split: c08bb14406

Seializing Vec<u8> by default iterate over each element instead of copying
the byte array.

See: https://github.com/rust-lang/rust/issues/31844

Map shared memory region as read-only in receiver

The maintainer of the `shared_memory` crate did not react to our PR, so I decided to create a (temporary) fork.

Make dataflow descriptor available to Python nodes and operators

The `with_extension` method returns a new path, it does not modify the existing path.

The previous watchdog requests required waiting for a reply, which could slow down the system under load and also lead to false errors on slower systems (e.g. the CI). Because of this, this commit replaces the watchdog requests with asynchronous heartbeat messages, which don't require replies. Instead, we record the last heartbeat timestamp whenever we receive a heartbeat message. We then periodically check the time since the last received heartbeat message and consider the connection closed if too much time has passed.

We synchronize the start of nodes (even across machines) to avoid missed messages. This led to deadlock issues when nodes exited before they initialized the connection to the dora daemon. The reason was that the other nodes were still waiting for the stopped node to become ready.

This commit fixes this issue by properly handling node exits that occur before sending the subscribe message. If nodes exit, they are removed from the pending list and added to a new  'exited before init' list. Once all nodes have subscribed or exited, we answer the pending subscribe requests. If nodes exited before subscribing we send an error reply to the other nodes because a synchronized start is no longer possible.

To make this logic work across different machines too, we add a `success` field to the `AllNodesReady` message that the daemon sends to the coordinator. The coordinator forwards this flag to other daemons so that they can act accordingly.