[EKS] [request]: v1.metrics.eks.amazonaws.com endpoints does not accept common Prometheus Accept headers

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**Tell us about your request**
`v1.metrics.eks.amazonaws.com` endpoints as documented [here](https://docs.aws.amazon.com/eks/latest/userguide/view-raw-metrics.html), return a 406: Not Acceptable header if an `Accept` header is present and not one of `application/json`, `application/yaml`, `application/vnd.kubernetes.protobuf`.

Prometheus formatted metrics are none of these so I suspect this is coming from API Gateway or another part of the stack doing unnecessarily validation.

**Which service(s) is this request for?**
EKS

**Tell us about the problem you're trying to solve. What are you trying to do, and why is it hard?**
Common prometheus integrations set either `text/plain`, `application/openmetrics-text`, or a mixed combination thereof with versions weighted with the quality value syntax (e.g. `application/openmetrics-text;version=1.0.0,application/openmetrics-text;version=0.0.1;q=0.75,text/plain;version=0.0.4;q=0.5,*/*;q=0.1`)

**Are you currently working around this issue?**
Yes - manually setting the Accept header to one of the supported values.

**Additional context**
Using Datadog agent as our Prometheus scraper, however the same behaviour can be repoduced with a cURL command:
```
curl -k -H "Accept: application/openmetrics-text" -H "Authorization: Bearer $(cat /var/run/secrets/kubernetes.io/serviceaccount/token)" https://kubernetes.default.svc/apis/metrics.eksamazonaws.com/v1/kcm/container/metrics
```

EKS Server Version reported as `v1.30.6-eks-7f9249a` (reported platform version `eks.20`)

Start with the AWS EKS raw metrics documentation and reproduce the 406 response using the provided curl command against the v1.metrics.eks.amazonaws.com endpoint. Investigate which EKS or API Gateway layer validates the Accept header; done means Prometheus headers such as text/plain and application/openmetrics-text return metrics without requiring a workaround.

Written by the indexing model from the issue text.