Gateway API: generate "standard" versions of install manifests

[skriss]

Currently, Contour uses the experimental Gateway API channel when generating its YAML manifests. However, with Gateway API v1.0 approaching, many users may prefer only to use the standard channel resources. This is already possible with Contour, by installing the standard Gateway API channel separately and then disabling the non-standard resources using CLI flags to contour serve. It'd be nice if we could provide this out of the box by generating a standard channel-based version of the YAML, that includes setting those CLI flags. The experimental version should remain available as well for folks who prefer to stay on the bleeding edge.

Note, #5276 is a partial blocker to doing this for the Gateway provisioner since we don't currently have a way to disable the experimental resources for dynamically provisioned contour gateways.

[lubronzhan]

#5276
This one is finished, now I can pick up this

[github-actions]

The Contour project currently lacks enough contributors to adequately respond to all Issues.

This bot triages Issues according to the following rules:

• After 60d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, the Issue is closed

You can:

• Mark this Issue as fresh by commenting
• Close this Issue
• Offer to help out with triage

Please send feedback to the #contour channel in the Kubernetes Slack

[github-actions]

The Contour project currently lacks enough contributors to adequately respond to all Issues.

This bot triages Issues according to the following rules:

• After 60d of inactivity, lifecycle/stale is applied
• After 30d of inactivity since lifecycle/stale was applied, the Issue is closed

You can:

• Mark this Issue as fresh by commenting
• Close this Issue
• Offer to help out with triage

Please send feedback to the #contour channel in the Kubernetes Slack