[BUG] requestHeaderConfiguration is missing from .bedrock_agentcore.yaml config file

**Describe the bug**
**requestHeaderConfiguration** is missing from _.bedrock_agentcore.yaml_ config file, however boto3 BedrockAgentCoreControlPlaneFrontingLayer.Client.create_agent_runtime(**kwargs) supports it.

**To Reproduce**
Edit .bedrock_agentcore.yaml and add the following:
requestHeaderConfiguration:
allowedHeaders:
- Authorization

**Expected behavior**
Expected behavior is setting up allowedHeaders and get it form AgentCoreRuntime context

Start with .bedrock_agentcore.yaml and the create_agent_runtime(**kwargs) entry point mentioned in the report. Verify that requestHeaderConfiguration.allowedHeaders can be declared there and is available from AgentCoreRuntime context; done when the Authorization example is accepted and exposed as expected.

Written by the indexing model from the issue text.