Improve PoE throughput and latency for some usecases

[alex-luxonis]

See details on related PR: luxonis/depthai-core#428

Usage example for the new options:

config = dai.Device.Config()
# config.board.network.mtu = 9000 # Not advised to increase past 1500 for now, may require bootloader changes
config.board.network.xlinkTcpNoDelay = False  # Default: True
config.board.sysctl = [
    'net.inet.tcp.delayed_ack=1',  # Default: 0
]

# Connect to device and start pipeline
with dai.Device(config) as device:
    device.startPipeline(pipeline)
...

[themarpe]

@Erol444 - Please document the above in appropriate section (could do in same PR if time permits)