expose redirect uri to oidc API

[zhaohuabing]

What this PR does / why we need it:

The current OIDC implementation uses a fixed redirect url: /oauth2/callback. It causes problem if this url doesn't match the HTTPRoute because the oauth2 filter can not receive the callback form the OIDC provider.

This PR exposes redirect uri to oidc API to make it possible to set the redirect uri to match the HTTPRoute url. For example:

HTTPRoute

kind: HTTPRoute
metadata:
  name: backend
spec:
  hostnames:
  - www.example.com
  parentRefs:
  - group: gateway.networking.k8s.io
    kind: Gateway
    name: eg
  rules:
  - matches:
    - path:
        type: PathPrefix
        value: /    # the current default redirect uri will be caught by this route, which has no oauth2 filter in its configuration.
    backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000
  - matches:
    - path:
        type: PathPrefix
        value: /secret-page
    backendRefs:
    - group: ""
      kind: Service
      name: backend
      port: 3000

SecurityPolicy

apiVersion: gateway.envoyproxy.io/v1alpha1
kind: SecurityPolicy
metadata:
  name: oidc-example
spec:
  oidc:
    # set redirect_uri to `/secret-page/oauth2/callback` to make sure the redirect from the OIDC provider can reach the correct HTTPRoute 
    redirect_uri: /secret-page/oauth2/callback 
    clientID: 250344188863-uve9br9mtrj05j2tfn8ls7n3fhemg3sr.apps.googleusercontent.com
    clientSecret:
      group: ""
      kind: Secret
      name: my-app-client-secret
    provider:
      issuer: https://accounts.google.com
  targetRef:
    group: gateway.networking.k8s.io
    kind: HTTPRoute
    name: backend

fix: #2326

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (38a3399) 64.66% compared to head (8133ba4) 64.66%.

❗ Current head 8133ba4 differs from pull request most recent head 6ca792e. Consider uploading reports for the commit 6ca792e to get more accurate results

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2370   +/-   ##
=======================================
  Coverage   64.66%   64.66%           
=======================================
  Files         114      114           
  Lines       16616    16631   +15     
=======================================
+ Hits        10744    10755   +11     
- Misses       5195     5197    +2     
- Partials      677      679    +2     

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