[ENHANCEMENT] - Add invoke_agent wrapper to BedrockInstrumentor()

[hakantekgul]

Right now, BedrockInstrumentor only collects telemetry data from invoke_model() under Bedrock. Bedrock recently released a multi-agentic SDK where users can use invoke_agent. Ideally, BedrockInstrumentor should also collect these agentic traces under the hood.

Example:
response = self.client.invoke_agent( agentAliasId=self.agent_alias_id, agentId=self.agent_id, enableTrace=True, inputText=input_text, memoryId=memory_id, sessionId=session_id, sessionState=session_state, )