Regression tests covering enum_virtual_ops API call
Prepare regression tests for enum_virtual_ops covering corner cases. For example case where iteration was splitted for block vops. Example query:
{"jsonrpc": "2.0", "method": "call", "params": ["account_history_api","enum_virtual_ops",
{
"block_range_begin": 2889020, "block_range_end": 2889021
, "operation_begin": 0, "limit": 10} ], "id": 1}
```
i.e. this call returned
"next_block_range_begin": 2889020, "next_operation_begin": "9223372036857428957"
and ID of next operation shall point to some different one than already processed.