Inject IAM Roles Anywhere credentials into pod running on EKSA Cluster

**What would you like to be added**:

We have EKS Pod identity webhook that injects IAM credentials into pod running on EKSA cluster.

This allows granular per pod/deployment credentials configuration.

Considering EKSA is deployed on on-premise, we want to have IAM Roles anywhere credentials injector for pods.

**Why is this needed**:

For security purposes to get granular IAM credentials on pod level.

Workaround:

```
./aws_signing_helper credential-process \
--certificate /path/to/certificate.pem \
--private-key /path/to/private-key.pem \
--trust-anchor-arn \
--profile-arn \
--role-arn
```

Run above script as init container for application pod and store the credentials in a config file.

configure application to parse these credentails and authenticate with AWS cloud.

Start by reviewing how the EKS Pod Identity webhook injects credentials into pods and how the `aws_signing_helper` is used in the documented init-container workaround. Define the injector’s pod-level configuration and credential delivery behavior for EKS Anywhere; done means applications can obtain IAM Roles Anywhere credentials without manually writing a config file.

Written by the indexing model from the issue text.