Artificial upper limit

Assertion in hive/libraries/plugins/apis/account_history_api/account_history_api.cpp:177 creates artificial bound while searching (by iterating) over rocksdb. This makes some operations vanish. Example:

{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "account_history_api.get_account_history",
    "params": {"account":"ned","operation_filter_low": 16, "start": 15452, "limit": 2}
}

Sending this JSON to hived, it returns one item, however matching operation (that will not exceed the limit) exists in block 4373677. To get that operation send this:

{
    "jsonrpc": "2.0",
    "id": 1,
    "method": "account_history_api.get_account_history",
    "params": {"account":"ned","operation_filter_low": 16, "start": 12452, "limit": 2}
}

Issue related to tests:

tavern/account_history_api_patterns/get_account_history/withdraw_vesting_operation.tavern.yaml::Hived
tavern/account_history_api_patterns/get_account_history/vote_operation.tavern.yaml::Hived
tavern/account_history_api_patterns/get_account_history/effective_comment_vote_operation.tavern.yaml::Hived
tavern/account_history_api_patterns/get_account_history/feed_publish_operation.tavern.yaml::Hived

@Trela @bwrona