[EKS] [eks-pod-identity] [bug]: Setting the STS Session name in eks-pod-identity-agent

I think this is probably more of a bug report, but I cannot find the proper channels.
Version Info:
EKS: 1.29
Eks Pod ID agent: v1.2.0-eksbuild.1

We are using eks-pod-identity. It's been working great till we started using IAM based kafka.

I directly hit the eks-pod-identity pod inside a container agent via
```
AWS_CONTAINER_CREDENTIALS_FULL_URI: http://169.254.170.23/v1/credentials
AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE: /var/run/secrets/pods.eks.amazonaws.com/serviceaccount/eks-pod-identity-token │
```

I took the resulting AccessKey, SecertKey, and Token, and used them to do a `aws sts get-caller-identity`

```
{
"UserId": "AROAXYZP66II6MSBPLOUU:eks-k8s-wl-dev-engine-boo-5af5e7ac-5754-49ea-b28f-2c2a2eb95fbb",
"Account": "BLAH",
"Arn": "arn:aws:sts::BLAH:assumed-role/dev-use1-default-bookingApiPod-20240529171038526700000001/eks-k8s-wl-dev-engine-boo-5af5e7ac-5754-49ea-b28f-2c2a2eb95fbb"
}
```

The SessionName is non static, and I can't find any way to force set it. The issue comes from the MSK IAM usage. MSK doesn't allow "reauthentication". We get this error when the session name changes
```
failed authentication due to: Cannot change principals during re-authentication from IAM.arn:aws:sts::BLAH:assumed-role/prd-use1-default-bookingApiPod-20240529174141238800000002/eks-k8s-wl-prd-engine-boo-064f1ed1-2349-4774-b895-9a69ccc3eeb1: IAM.arn:aws:sts::BLAH:assumed-role/prd-use1-default-bookingApiPod-20240529174141238800000002/eks-k8s-wl-prd-engine-boo-875fdfcd-19cd-4ac3-8544-7077f94a6e39
```

Most services we've used IAM for to date don't care. The solution normally would be to set `AWS_ROLE_SESSION_NAME` when calling STS:AssumeRole. But we're not calling that, the eks-pod-identity pod is. The ContainerCredentialProvider in the SDK is just calling the `AWS_CONTAINER_CREDENTIALS_FULL_URI` URL with the contents of `AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE` as the Authorization header. There is no option as far as I've found to have that include a constant session name to satisfy MSK.

Thanks!

Start by tracing the eks-pod-identity pod's credential endpoint and the ContainerCredentialProvider flow using AWS_CONTAINER_CREDENTIALS_FULL_URI and AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE; the issue names no source files or tests. Review how the agent obtains credentials through STS and how MSK IAM handles reauthentication. Done means a supported way exists to keep the STS session name stable for this workflow.

Written by the indexing model from the issue text.