Gateway api state metrics

[Ygnas]

Closes: #438

Verification

1. export MGC_BRANCH=gateway-api-state-metrics

   Before running quickstart-metrics make sure that resources exist Multicluster Gateways Walkthrough

2. curl -sS https://raw.githubusercontent.com/Ygnas/multicluster-gateway-controller/gateway-api-state-metrics/hack/quickstart-metrics.sh | bash

   Note: The default login credentials for Grafana are admin/admin. You may need to accept the non-CA signed certificate to proceed.

3. Should be able to see the new dashboards Grafana
   

[david-martin]

/lgtm
/approve

OK to land after the release merge blocker.

[openshift-ci]

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[david-martin]

Merging despite the merge blocker issue for the release as these changes are isolated to the quickstart metrics script and the metrics walkthrough.
No other testing, expect for what's been done for this issue, has been executed for the release so it makes sense to have tested and verified content for metrics for the release.