Clean up the code for network connection

[wh201906]

• Move uart_bind() to uart_common.c, as most of the code in it is platform-independent.
• Add const qualifier to some arguments of uart_bind()
• Refactor the address/port parser into a separate function uart_parse_address_port(). This code block was repeated 8 times in the old implementation.
• Merge the code of TCP and UDP connection in uart_open()
• Add some code to check the prefix length before calling memcmp()

[github-actions[bot]]

You are welcome to add an entry to the CHANGELOG.md as well

[iceman1001]

Excellent refactoring!