Provide custom proxy path for dynamic plugins

Dynamic plugins must access proxies using the namespace, name, and port of proxied services, in the following format:

/api/proxy/namespace/<namespace>/service/<name>:<port>

Because these values might only be known at installation time, it would be helpful to be able to access these proxies via an alias or path that could be fixed. For example, if the ConsolePlugin was specified as follows:

apiVersion: console.openshift.io/v1alpha1
kind: ConsolePlugin
metadata:
  name: acm-console-plugin
spec:
  displayName: Red Hat Advanced Cluster Management
  proxy:
    services:
      - authorize: true
        name: console-chart-9bc0f-console-v2
        namespace: open-cluster-management
        port: 3000
        path: acm-proxy
  service:
    basePath: /plugin/
    name: console-chart-9bc0f-console-v2
    namespace: open-cluster-management
    port: 3000 

Then the proxy could be accessed via:

/api/proxy/<plugin-name>/<proxy-path> ie. /api/proxy/acm-console-plugin/acm-proxy