Allow for label values that match multiple selectors

[m90]

Discussed in #620

^{Originally posted by huyz August 15, 2025}
If I have a list of labels like docker-volume-backup.stop-during-backup=label1 and docker-volume-backup.stop-during-backup=label2, would either label cause the container to stop. I'm not sure how valid it is to have labels with the same key

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How it could be done:

• come up with a good new label name whose value is being split on commas automatically
• keep the old behavior for the old label name, but print a deprecation warning on usage
• remove all mentions of the old label from the docs
• on the next major version, remove the old label entirely

or:

• introduce a LABEL_MATCH_BEHAVIOR which defaults to MATCH which is what is happening right now
• when this is set to ONE_OF, start splitting values on commas

I'm only 98% sure this can be done right now, as filtering by labels is rather restricted in Docker and adding this feature might mean we'd have to reimplement matching from scratch ourselves.