[BUG] Remove `dataStoreORMGetIdentifiers` methods

[mirceanis]

The existing IDataStoreORM interface defines 2 methods (dataStoreORMGetIdentifiers and dataStoreORMGetIdentifiersCount) that theoretically provide the ability to query for DIDs based on the did value, the alias or the provider. However, this is based on the assumption that the IDIDManager plugin, or to be more precise the AbstractDIDStore implementation uses the same database as the IDataStore/IDataStoreORM plugin implementations.

There is also the assumption that saving a credential, presentation or message to the database would automatically link it to the respective DID, or add new partial IIdentifier entries based on issuer/subject, holder/verifier, from/to properties of the idem being added, and that deleting such an identifier would also automatically delete the data related to it.

These are separate concerns, so the IDataStoreORM interface should not require these methods to be implemented, nor that the data related to a particular identifier is automatically deleted.

The methods are marked as deprecated and should be removed in Veramo 4.x

• [ ] remove dataStoreORMGetIdentifiers and dataStoreORMGetIdentifiersCount from IDataStoreORM interface
• [ ] remove dataStoreORMGetIdentifiers and dataStoreORMGetIdentifiersCount from @veramo/data-store
• [ ] remove IIdentifier foreign keys from the respective @veramo/data-store#Entities
• [ ] add migration to remove cascading
• [ ] add test to check migration from earlier database version
• [ ] remove dataStoreORMGetIdentifiers and dataStoreORMGetIdentifiersCount from @veramo/data-store-json
• [ ] add test to ensure that data other does not get deleted along with an IIdentifier entry.