Make auth package indepent from eventpolicy informer

[creydr]

Currently the pkg/auth package depends on the eventpolicy informer (through the tokenverifier), requiring everything what imports knative.dev/eventing/pkg/auth to have permissions to read&list EventPolicies.
This leads to the following issues e.g. for PingSource (which does not need the TokenVerifier):

W0916 14:29:26.690900       1 reflector.go:547] k8s.io/client-go@v0.30.3/tools/cache/reflector.go:232: failed to list *v1alpha1.EventPolicy: eventpolicies.eventing.knative.dev is forbidden: User "system:serviceaccount:knative-eventing:pingsource-mt-adapter" cannot list resource "eventpolicies" in API group "eventing.knative.dev" at the cluster scope
E0916 14:29:26.690991       1 reflector.go:150] k8s.io/client-go@v0.30.3/tools/cache/reflector.go:232: Failed to watch *v1alpha1.EventPolicy: failed to list *v1alpha1.EventPolicy: eventpolicies.eventing.knative.dev is forbidden: User "system:serviceaccount:knative-eventing:pingsource-mt-adapter" cannot list resource "eventpolicies" in API group "eventing.knative.dev" at the cluster scope

This PR addresses it and removes the dependency in the TokenVerifier to the EventPolicy informer. In addition it renames the auth.OIDCTokenVerifier to auth.Verifier as this includes AuthN and AuthZ.

[codecov]

Codecov Report

Attention: Patch coverage is 18.51852% with 22 lines in your changes missing coverage. Please review.

Project coverage is 67.48%. Comparing base (ae6ed99) to head (a459dc2).
Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/auth/verifier.go	0.00%	11 Missing ⚠️
cmd/jobsink/main.go	0.00%	6 Missing ⚠️
cmd/broker/filter/main.go	0.00%	2 Missing ⚠️
cmd/broker/ingress/main.go	0.00%	2 Missing ⚠️
pkg/channel/event_receiver.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8195      +/-   ##
==========================================
+ Coverage   67.47%   67.48%   +0.01%     
==========================================
  Files         371      371              
  Lines       18036    18036              
==========================================
+ Hits        12169    12171       +2     
+ Misses       5088     5087       -1     
+ Partials      779      778       -1     

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[pierDipi]

/lgtm

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: creydr, pierDipi

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