Support Peak EWMA load balancing policy in Envoy Gateway

[kahirokunn]

Description:
A PR to add Peak EWMA load balancing to Envoy is currently under review.
Once this is merged, it would be valuable to expose Peak EWMA as a load balancing option in Envoy Gateway as well.

Motivation:

• Ensure Envoy Gateway can make use of new load balancing policies introduced in Envoy
• Provide users with more choices for traffic distribution strategies

[zirain]

I think we probably need to wait it be part of envoy core instead of contrib.

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.

[kahirokunn]

keep

[github-actions]

This issue has been automatically marked as stale because it has not had activity in the last 30 days.

[kahirokunn]

keep