Add support for OpenAI API streaming protocol

[kfswain]

Adding support for OpenAI API streaming, we are currently skipping extraction of the usage metrics. That will be more generally solved here #329.

[netlify]

✅ Deploy Preview for gateway-api-inference-extension ready!

Name	Link
🔨 Latest commit	0d76e00
🔍 Latest deploy log	https://app.netlify.com/sites/gateway-api-inference-extension/deploys/67d1edca5f498f00081630f3
😎 Deploy Preview	https://deploy-preview-469--gateway-api-inference-extension.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify site configuration.

[ahg-g]

/lgtm
/approve

Thanks for the great test coverage!

[k8s-ci-robot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: ahg-g, kfswain

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [ahg-g,kfswain]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment