silence-operator release v0.8.0

Add .svc suffix to the alertmanager address to make silence operator work behind a corporate proxy.
Upgrade to go 1.19
Bump github.com/spf13/cobra from 1.4.0 to 1.5.0.
Bump github.com/spf13/cobra from 1.6.0 to 1.6.1
Bump sigs.k8s.io/controller-runtime from 0.12.2 to 0.12.3
Bump sigs.k8s.io/controller-runtime from 0.12.3 to 0.13.0
Bump sigs.k8s.io/controller-runtime from 0.13.0 to 0.13.1
Bump alpine from 3.16.0 to 3.17.1
Bump github.com/prometheus/client_golang from 1.12.2 to 1.13.0
Bump github.com/prometheus/client_golang from 1.13.1 to 1.14.0
Bump github.com/giantswarm/k8smetadata from 0.11.1 to 0.13.0
Reconcile API if Silence CR gets updated
Deprecate PostmortemURL field in favour of IssueURL.
Make Silence Owner field a string instead of string pointer.
Bump golang.org/x/text from v0.3.7 to v0.3.8
Bump github.com/nats-io/nats-server from v2.5.0 to v2.9.3
Bump github.com/getsentry/sentry-go from v0.11.0 to v0.14.0