Allow more granular assignment of metadata (e.g. node) to scrape and collection targets #971
Description
The metadata watching mechanism allows configuring label additions at the global and collection-target level, but not at the individual target/source level.
A use case for this is opting out of metadata addition for common/shared pods like cluster-wide kube-state-metrics pods. They are commonly used for pod metrics and attaching the node metadata from the kube-state-metrics node and not the pod's node is confusing for users. There is not really a generalized way to traverse these metrics as we get them to map to the appropriate node, so better to allow excluding these pods from this metadata.
ServiceMonitors in prometheus-operator solve this by opting-in to node metadata at the scrape target level with the attachMetadata.node configuration.