opentelemetry-opamp-client 0.6b0

Added

• opentelemetry-opamp-client: accept an AgentToServer message in OpAMPAgent.send() and add OpAMPClient.prepare_message() (#5107)

Changed

• opentelemetry-opamp-client: the OpAMPClient.build_*_message() methods return an AgentToServer message instead of bytes; its instance UID and sequence number are set when it is sent (#5107)

Fixed

• opentelemetry-opamp-client: adopt the instance UID assigned by the server (#5096)
• opentelemetry-opamp-client: fix repeated sequence numbers and gaps after retries (#5107)
• opentelemetry-opamp-client: send the instance UID HTTP header matching each message (#5285)
• Retry the initial state report until a response is received or shutdown interrupts it, enabling heartbeats only after a response and preserving completion callbacks for failed sends. (#5287)