Transport Asynchronization

[yellowhatter]

Description

Asynchronization work for zenoh-transport

What does this PR do?

• Make sure that asynchronous API calls and rx calls of the routing that lead to message emissions do push those messages to the pipelines asynchronously.

• Make the pipeline push operation(s) asynchronous. Note: the pipeline historically had synchronous push operations, some inspiration could be get there if needed.

• Make the primitive functions asynchronous.

• Make the routing code return futures that send needed messages to needed destinations when awaited. Note: messages to different destinations may be sent in parallel (not mandatory) but messages to the same destination must be sent in sequence.

• Make sure asynchronous calls in the API do return futures from the primitives when some.

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🏷️ Label-Based Checklist

Based on the labels applied to this PR, please complete these additional requirements:

Labels: enhancement

✨ Enhancement Requirements

Since this PR enhances existing functionality:

• Enhancement scope documented - Clear description of what is being improved
• Minimum necessary code - Implementation is as simple as possible, doesn't overcomplicate the system
• Backwards compatible - Existing code/APIs still work unchanged
• No new APIs added - Only improving existing functionality
• Tests updated - Existing tests pass, new test cases added if needed
• Performance improvement measured - If applicable, before/after metrics provided
• Documentation updated - Existing docs updated to reflect improvements
• User impact documented - How users benefit from this enhancement

Remember: Enhancements should not introduce new APIs or breaking changes.

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