Major re-org to crate / repository structure

[Carter12s]

Description

A major re-organization of the components of roslibrust per: https://github.com/orgs/RosLibRust/discussions/214

Some facets of this:

• The core roslibrust crate now includes no backends by default. The rosbridge backend is now hidden behind the rosbridge feature flag. This means you don't pay to compile any backend that you aren't using.
• The rosbridge backend moved under the rosbridge namespace in the roslibrust crate so it is no longer treated as a special backend in the naming conventions.
• RosApi trait and implementations moved out of roslibrust and into their own crate. Also now generically written so they can be used with any backend.

Fixes

Closes: number

Checklist

• Update CHANGELOG.md

[Carter12s]

@lucasw / @ssnover this is ready for a review now.

It is a pretty big change to overall crate structure, but I think aligns things much more where I want development to head.

I think it sets things up well to eventually include a ros2 backend with either zenoh or dds, and I think it sets us up very well to start making the generic traits for TopicProvider and ServiceProvider the a first class API that both allows folks to swap backends around and to use MockRos for testing.

[ssnover]

Reading on mobile right now, but just going to ask clarifying questions and I'll review later:

• Is the intended entry point crate roslibrust_common now?
• Should it maybe be called roslibrust_core?

[Carter12s]

For users the intended entrypoint is still roslibrust

The "standard" usage would be to depend on roslibrust with at least one backend enabled via a feature flag.

Depending on roslibrust with no backends enabled can be done (see rosapi) to implement generic behaviors without a particular backend specified as well.

Not expecting anyone outside of roslibrust development to depend on roslibrust_common and I'm super happy to rename that to roslibrust_core or potentially roslibrust_traits <- that is most specifically what is actually inside it at the moment.

[Carter12s]

Flagging for myself I still need to clean this up before merge

[ssnover]

Mostly nitpicks and questions about tracking todos.

[ssnover]

Since integration tests will have similar visibility to internals as user code, I think it's probably best for the integration test to look like what we expect it to look like for users; i.e. keep roslibrust::ros1::

[ssnover]

Oh looking at this now, I see this is under src instead of tests which is where integration tests ought to go (since they have the same visibility into the crate as a user of the crate does).

[Carter12s]

Good catch I'll re-org!

[ssnover]

This is an aside, but perhaps:

let md5sum = roslibrust_common::md5sum::message_definition_to_md5sum(
    topic_type,
    msg_definition
).map_err(|err| {
    log::error!("{err:?}");
    Err(NodeError::IoError(io::ErrorKind::ConnectionAborted.into()))
})?;

[ssnover]

It might be nice to change the name of message_definition_to_md5sum to from_message_definition since it's already namespaced under md5sum module.