Requests for catalog delayed

[absoludity]

Describe the bug
While testing #4918 , I noticed an oddity that is causing requests for GetAvailablePackageSummaries to be delayed significantly (up to 16s sometimes:

While watching the logs for pinniped proxy, I see the delay is because every request is creating a new REST API mapper and I suspect it's being throttled. What I see is that each paginated request results in a bunch of requests to the APi server:

INFO  pinniped_proxy::expired_value_cache > cache hit
 INFO  pinniped_proxy::expired_value_cache > cache hit
 INFO  pinniped_proxy::expired_value_cache > cache hit
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/autoscaling/v2beta2?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/scheduling.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/batch/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/kubeapps.com/v1alpha1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/authentication.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/autoscaling/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/apps/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/discovery.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/events.k8s.io/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/coordination.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/batch/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/flowcontrol.apiserver.k8s.io/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/autoscaling/v2?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/node.k8s.io/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/storage.k8s.io/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/node.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/apiregistration.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/certificates.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/events.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/api/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/storage.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/flowcontrol.apiserver.k8s.io/v1beta2?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/authorization.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/discovery.k8s.io/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/policy/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/apiextensions.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/admissionregistration.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/config.concierge.pinniped.dev/v1alpha1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/identity.concierge.pinniped.dev/v1alpha1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/networking.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/policy/v1beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/autoscaling/v2beta1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/authentication.concierge.pinniped.dev/v1alpha1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/rbac.authorization.k8s.io/v1?timeout=32s 200 OK
 INFO  pinniped_proxy::service             > GET https://kubernetes.default/apis/login.concierge.pinniped.dev/v1alpha1?timeout=32s 200 OK
 INFO  pinniped_proxy::expired_value_cache > cache hit
 INFO  pinniped_proxy::service             > POST https://kubernetes.default/apis/authorization.k8s.io/v1/selfsubjectaccessreviews 201 Created

and for each paginated request, it takes longer.

To Reproduce
Steps to reproduce the behavior:

1. install kubeapps with pinniped setup
2. Follow logs for the pinniped-proxy container
3. Access the catalog (when the bitnami repo is installed as it is by default)
4. See error

Expected behavior
Each page should be returned promptly, and there should not be multiple requests to generate the rest mapper (perhaps we need to cache this per token, not sure yet).

[absoludity]

Need to investigate whether this is just affecting the pinniped setup (I assume so, since I've not seen it before and have been testing this pagination quite a bit lately), and if so, why.