[INLONG-126] Increase the unflushed data bytes control

[dockerzhang]

Currently, there are unflushThreshold indicating the number of unwashed disks and unflushInterval indicating the maximum interval of unwashed disks. Through analysis, data flushing check should increase the unflushed data bytes control:

The unflushed indicators are setted to threshold to monitor and make the possibility of data loss of within the controllable range, but the time interval and the number of messages are not enough, for example, the same 1000 messages, in the case of a 100-byte message and a 512K-byte message, we not only need to check the number of entries, but also need to check the accumulated total data size of the unwashed disk

For this problem, the new version plans to adjust to increase the unflushDataSize indicator.

JIRA link - [INLONG-126] created by gosonzhang