[feat] Add instrumentation for official A2A

[lyred193]

https://github.com/a2aproject/a2a-python

[ralf0131]

A2A protocol is going to be donated to Linux Foundation https://www.linuxfoundation.org/press/linux-foundation-launches-the-agent2agent-protocol-project-to-enable-secure-intelligent-communication-between-ai-agents

That is surely what we would like to support.