[V2] Enable metrics server

[rquitales]

Proposed changes

This PR exposes the metrics service in our manifests and adds new unit tests to ensure the metrics logic is correct.

Technical changes

1. Added sigs.k8s.io/controller-runtime/pkg/metrics/filters dependency to allow metrics to be secure by default (guidance from kubebuilder book/scaffold)
2. Adds new kustomize patches and bases to expose the metrics server in a typical PKO deployment
3. Refactor the updateStackCallback function
4. Added the stacks_reconciling metric
5. Added ginkgo tests to exercise the Program and Stack metrics
6. Fixed some bugs in our metrics as determined through the unit tests

Testing

• Manually tested a deployed PKO installation with the Prometheus Operator
• Added unit tests (using ginkgo)

Note, e2e tests will be added in a followup PR.

Related issues (optional)

Closes: #576

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 67.27273% with 18 lines in your changes missing coverage. Please review.

Project coverage is 50.22%. Comparing base (2a67d4c) to head (2bc40ee). Report is 1 commits behind head on v2.

Files with missing lines	Patch %	Lines
operator/cmd/main.go	0.00%	12 Missing :warning:
...erator/internal/controller/pulumi/metrics_stack.go	88.23%	2 Missing and 2 partials :warning:
operator/internal/controller/pulumi/utils.go	60.00%	1 Missing and 1 partial :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## v2 #706 +/- ## ========================================== + Coverage 49.57% 50.22% +0.65% ========================================== Files 27 27 Lines 2911 2919 +8 ========================================== + Hits 1443 1466 +23 + Misses 1290 1272 -18 - Partials 178 181 +3 ```

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