add prometheus metrics to count PE resolving errors

[haouc]

What type of PR is this?

improvement
Which issue does this PR fix:
Add prometheus support for customized metrics. In this PR, we add metrics from policy endpoints resolving errors.

What does this PR do / Why do we need it:
We should have better observability on how policy endpoints have been resolved.

If an issue # is not available please add steps to reproduce and the controller logs:

Testing done on this change:

Tested in dev cluster with a new deployment.

# HELP cleanup_network_policy_endpoints_err_count The number of errors encountered while cleaning up network policy endpoints
# TYPE cleanup_network_policy_endpoints_err_count counter
cleanup_network_policy_endpoints_err_count 0
# HELP compute_egress_endpoints_err_count The number of errors encountered while computing egress endpoints
# TYPE compute_egress_endpoints_err_count counter
compute_egress_endpoints_err_count 0
# HELP compute_ingress_endpoints_err_count The number of errors encountered while computing ingress endpoints
# TYPE compute_ingress_endpoints_err_count counter
compute_ingress_endpoints_err_count 0
# HELP compute_pod_endpoints_err_count The number of errors encountered while computing pod endpoints
# TYPE compute_pod_endpoints_err_count counter
compute_pod_endpoints_err_count 0

Automation added to e2e:

Will this PR introduce any new dependencies?:

Will this break upgrades or downgrades. Has updating a running cluster been tested?:

Does this PR introduce any user-facing change?:

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.