ProviderIdSet produces no events for providers being added or removed

This makes it more difficult to index provider endorsement status. It probably should be added to make it easier to recognise when the state of the world has changed.

The payload names no files or tests. Locate the ProviderIdSet implementation and inspect the existing paths where providers are added or removed. Done means those transitions emit observable events that an indexer can use to recognize provider endorsement status changes.

Written by the indexing model from the issue text.