Historical queries handles may implicitly overlap

[maxtropets]

Historical adapter uses get_state_at(handle=seqno, seqno=seqno), and also calls populate_service_endorsements and populate_cose_service_endorsements in the same way.

Historical cache is exposed to the user, as well as get_state_at calls. It may happen that both framework code (inside the adapter) and user code will end up using same handle for different seqnos.

I see two possible solutions

• adapter has to provide a way for user to control the handle
• adapter shall use CompoundHandle (System, seqno)

The second option seems simpler and more straightforward to me.