Add possibility to use serial over network

[cziter15]

ABOUT THIS PR
I've been working on my own Zigbee Gateway project and this script was really helpful in context of flashing. However, as my project is ESP32S3 based I preferred to use WiFi and that's why I've modiffied this script to support over-the-air flashing.

Changes done within this PR:

• added Serial Over Socket support, use 'socket://' in as prefix for Serial Port Name -p socket://<ip or local domain>:<port>
• added mode parameter '-m','--mode' which deaults to 'autobtl' (auto bootloader), the other mode is 'xmodem' (see below for details)

Few words aboutr -m / --mode:

• Elelabs modules can be reset via NCP command ('autobtl' mode), which means whole flow will be handled automatically
• There are some other modules on the market which can be reset using external pin (that's why there's XMODEM mode)
• In case of external pin, the 'xmodem' mode tells the script to skip all the probing and try to flash immediately

EXAMPLES:

• Flashing the module with exposed xmodem interface on target serial port

python Elelabs_EzspFwUtility.py flash -f efr32mg1b-v8-6910-115200.gbl -p socket://mygateway.local:19020 -d RAW -m xmodem

• Remote probe call

python Elelabs_EzspFwUtility.py probe -p socket://mygateway.local:19020 -d RAW