【Feature Suggestions】Add Mux multiplexing and node connection monitoring features

[jiegengxiangjianxue]

1. Mux Multiplexing Settings

• Added a master switch, which is off by default with a prompt saying "Can reduce latency but carries risk of disconnection"
• Supports configuring the number of TCP and XUDP multiplexed subconnections separately
• Allows selection of QUIC traffic processing mode (deny/direct connect/multiplex)

2. Observatory settings

• Supports customizing the leastPing detection interval
• Supports customizing the leastLoad detection interval, HTTP request method（HEAD、GET）, sample quantity, and detection timeout
• Better supports automatic node optimization and load scheduling