The templates for the mgr-generated ServiceMonitor and PrometheusRule objects included the labels
prometheus and team, making it impossible to override them as user.
This adds a new method `OverwriteApplyToObjectMeta` to
pkg/apis/ceph.rook.io/v1.Labels, which, contrary to the existing
`ApplyToObjectMeta` method, overwrites existing labels.
Closes: https://github.com/rook/rook/issues/8502
Signed-off-by: Mara Sophie Grosch <littlefox@lf-net.org>