add podmonitor to coredb spec

[ChuckHend]

adds metrics to AppService spec:

app_services:
  metrics:
    path: /metrics
    port: 3000

When this is present in the CoreDB Spec, Tembo Operator deploys a PodMonitor for the specified AppService, which will result in scraping metrics from the specified port and path.

The PodMonitor is owned by the Service associated with the AppService, so when the AppService is deleted, so is the Service and the PodMonitor.

[nhudson]

You might want to bump the controller version as well.