Handle deleting and updating data in the layer hosting location

[MattF-NSIDC]

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This may be OBE if we're going to drop support for the plugin.

Q: Do we care about zero-downtime? A: No, we can just run late at night for minimal impact when we're re-processing a layer.

How do we ensure we actually update the layers we intend to update? i.e. do we run a manual cleanup command with each release? Build some more tooling?