feat: Multiple Rate Limiting option (again)

[s0uky]

Description:
This feature request is follow up from Slack discussion with @arkodg .

The functionality for defining multiple rate limits was previously available through RateLimitFilters. However, these filters were removed from the codebase around version 0.6.0. A new CRD named BackendTrafficPolicy was introduced, and the rateLimit field now belongs to this CRD.

It would be beneficial to be able to define multiple rate limits again for entire paths within BackendTrafficPolicy. This would allow for a use case where a "basic" rate limit could be applied to unauthenticated clients, while a stricter "proper" rate limit could be applied to users with valid JWT authentication (basic authentication is a separate consideration).

[arkodg]

this should be possible with https://gateway.envoyproxy.io/docs/tasks/traffic/global-rate-limit/

Option 1 - match on :path
sometthing like

  rateLimit:
    type: Global
    global:
      rules:
      - clientSelectors:
        - headers:
          - name: :path
            value: /app
        limit:
          requests: 3
          unit: Hour

Option 2
Create 2 HTTPRoutes (same hostname but different rules for different path matches) and apply a unique BTP for each HTTPRoute

[arkodg]

keeping this issue open so we can consider adding path and method (relates to #4448) as first class fields in the API so users dont need to rely on the pseudo headers