Add server_is_available to ActionClientState

[patrick-deschambault]

Description

This PR adds the server_is_available method to ActionClientState.

Currently, rclrs action clients does not have a built-in mechanism to verify the availability of an action server on the network. This makes it difficult to safely send goals upon initialization without risking dropped requests.

By exposing the rcl_action_server_is_available binding, this PR enables developers to easily build reliable waiting logic.

Example Use Case

This enables the implementation of async timeout loops in user code, such as:

async fn wait_for_server(&self, timeout: std::time::Duration) -> Result<(), rclrs::RclrsError> {
    tokio::time::timeout(timeout, async {
        loop {
            if self.client.server_is_available()? {
                return Ok(());
            }
            tokio::time::sleep(std::time::Duration::from_millis(100)).await;
        }
    }).await.unwrap_or(Err(rclrs::RclrsError::Custom("Timeout".into())))
}

[esteve]

@patrick-deschambault thanks for the PR, can you elaborate why you needed this? Could you remove it if you don't need it? Thanks.

[patrick-deschambault]

My mistake ! Should be erased ( 3cf276e )

[esteve]

@patrick-deschambault CI is failing because the code is not formatted properly, could you run cargo fmt and fix the warnings? Thanks

[esteve]

It'd be really useful to provide tests for this function, could you add them?

[patrick-deschambault]

Yes sure, I'll put the PR on Draft and bring it Under Review when ready. Thanks for your input !