Allow more granular assignment of metadata (e.g. node) to scrape and collection targets

The [metadata watching mechanism](https://azure.github.io/adx-mon/config/#metadata-watching) 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.

Start with the metadata watching mechanism described in the linked configuration documentation, then compare its global and collection-target settings with prometheus-operator's ServiceMonitor attachMetadata.node configuration. The work is done when individual scrape targets or sources can control node metadata, including opting out for shared kube-state-metrics pods.

Written by the indexing model from the issue text.