Support channel URI migration

We support automatic migration of these channel URIs:

1. task.channel: when the task is to be executed,
2. case.modelContext.channel: when model context is deserialized (the channel is not changed in the case, only the updated value is fetched)
3. metadata (object, assignment, focus/projection password): when they are updated

We do NOT automatically migrate the following channel URIs:

1. in shadow synchronization situation description,
2. in task "actions executed" statistics,
3. in operation execution records,
4. in configuration: mapping.channel, mapping.exceptChannel, reaction.channel, authentication configuration.