Support authentication for cloud resources using IAM roles

**Problem**

We urgently need IAM role-based authentication for AWS resources, especially AWS MSK, within Knative Eventing. Currently, only username/password authentication is documented for MSK [here](https://knative.dev/docs/eventing/brokers/broker-types/kafka-broker/#set-as-default-broker-implementation)), which is less secure and cumbersome than IAM roles.

This feature is critical for our AWS integration and aligns with best practices. Is there an existing IAM authentication method I've missed? Are there plans to implement this? We're on AWS cloud and using Knative Eventing 1.17.4

This feature request is not just for MSK, but for supporting IAM based authentication for all the cloud resources.

**[Persona:](https://github.com/knative/eventing/blob/main/docs/personas.md)**
Which persona is this feature for?
System Operator

**Exit Criteria**
Authetication to cloud resources such as S3, MSK, cloudStorage using IAM role based access.

Start with the Kafka broker authentication documentation linked in the issue and compare its username/password approach with AWS IAM role requirements for MSK. Broaden the investigation to the requested S3 and cloud storage resources; done means IAM role-based authentication works for those cloud resources, including the stated MSK use case.

Written by the indexing model from the issue text.