🐛 Use uint32 for flush count packing

[AlexV525]

Traceback (most recent call last):
  File "/data/atomicals-electrumx/electrumx_server", line 47, in main
    asyncio.run(controller.run())
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.10/asyncio/base_events.py", line 649, in run_until_complete
    return future.result()
  File "/data/atomicals-electrumx/electrumx/lib/server_base.py", line 129, in run
    await server_task
  File "/data/atomicals-electrumx/electrumx/lib/server_base.py", line 102, in serve
    await self.serve(shutdown_event)
  File "/data/atomicals-electrumx/electrumx/server/controller.py", line 134, in serve
    async with OldTaskGroup() as group:
  File "/usr/local/lib/python3.10/dist-packages/aiorpcX-0.22.1-py3.10.egg/aiorpcx/curio.py", line 297, in __aexit__
    await self.join()
  File "/data/atomicals-electrumx/electrumx/lib/util.py", line 370, in join
    task.result()
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 3587, in fetch_and_process_blocks
    async with OldTaskGroup() as group:
  File "/usr/local/lib/python3.10/dist-packages/aiorpcX-0.22.1-py3.10.egg/aiorpcx/curio.py", line 297, in __aexit__
    await self.join()
  File "/data/atomicals-electrumx/electrumx/lib/util.py", line 370, in join
    task.result()
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 3540, in _process_prefetched_blocks
    await self._first_caught_up()
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 3556, in _first_caught_up
    await self.flush(True)
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 464, in flush
    await self.run_in_thread_with_lock(flush)
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 313, in run_in_thread_with_lock
    return await asyncio.shield(run_in_thread_locked())
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 312, in run_in_thread_locked
    return await run_in_thread(func, *args)
  File "/usr/local/lib/python3.10/dist-packages/aiorpcX-0.22.1-py3.10.egg/aiorpcx/curio.py", line 57, in run_in_thread
    return await get_event_loop().run_in_executor(None, func, *args)
  File "/usr/lib/python3.10/concurrent/futures/thread.py", line 58, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/data/atomicals-electrumx/electrumx/server/block_processor.py", line 462, in flush
    self.db.flush_dbs(self.flush_data(), flush_utxos,
  File "/data/atomicals-electrumx/electrumx/server/db.py", line 439, in flush_dbs
    self.flush_history()
  File "/data/atomicals-electrumx/electrumx/server/db.py", line 515, in flush_history
    self.history.flush()
  File "/data/atomicals-electrumx/electrumx/server/history.py", line 160, in flush
    flush_id = pack_be_uint16(self.flush_count)
struct.error: 'H' format requires 0 <= number <= 65535