Amazon Bedrock AgentCore Samples - [Token exchange via Gateway interceptors - realistic use case]

**Describe the tutorial request**
Token exchange example via Gateway Interceptor with realistic setup and terraform IaC that uses different client_ids to authenticate calls to AgentCore Gateway and API Gateway.

### Concise description of the PR

```
The current example does not show the correct header propagation, and requires Jupyter notebooks to deploy the solution which is not something developers use. This use case is not aimed to data scientists.
```

### User experience

> Please share what the user experience looks like before and after this change

Before: need to use Jupyter Notebook to deploy the infrastructure which is not a familiar tool for backend and full-stack developers. Token propagation is faked and the new token is sent as part of the payload instead of an auth header and correctly used.

After: use Terraform for IaC which is the mostly used IaC tool by our customer. Correctly propagate token to the Authorization header to the target and shows the full e2e auth flow.

**Is this feature already supported by the AgentCore service?**
- [ ] Yes
- [x] No

If `yes`, please provide any appropriate documentation link.