If an oracle node is resynchronized from the genesis the service receives all
requests from all blocks via AddRequests() invoked from the native
contract. Almost all of them are long obsolete and need to be removed, native
oracle contract will try to do that with RemoveRequests() calls, but they
won't change anything.
So queue up all "initial" requests in special map and manage it directly
before the module is Run() which happens after synchronization
completion. Then process any requests that are still active and work with new
blocks as usual.
1. Initialization is performed via `Blockchain` methods.
2. Native Oracle contract updates list of oracle nodes
and in-fly requests in `PostPersist`.
3. RPC uses Oracle module directly.
