Motivation:
When `consolidatedWhenNoReadInProgress` is true, `channel.writeAndFlush (data) .addListener (f-> channel.writeAndFlush (data2))` Will cause data2 to never be flushed.
Because the flush operation will synchronously execute the `channel.writeAndFlush (data2))` in the `listener`, and at this time, since the current execution thread is still an `eventloop`(`executor.inEventLoop()` was true), all handlers will be executed synchronously. At this time, since `nextScheduledFlush` is still not null, the `flush` operation of `data2` will be ignored in `FlushConsolidationHandler#scheduleFlush`.
Modification:
- reset `nextScheduledFlush` before `ctx.flush`
- use `ObjectUtil` to polish code
Result:
Fixes https://github.com/netty/netty/issues/9923
044b6b0661