FIX: [environment] change the semantic of sync symbols with prefix

[dboyliao]

This PR changes the behavior of sync symbols with prefixes to be session-specific, rather than additive to the global sync symbols.

Changes

Before:

• All sessions would sync the "rest symbols" (symbols without prefix) by default
• Session-specific symbols (with prefix like max:BTCUSDT) would be appended to the rest symbols
• This meant sessions with specific symbols would sync both their specific symbols AND all the rest symbols

After:

• Sessions with specific symbols defined will ONLY sync those symbols
• Sessions without specific symbols will sync all the "rest symbols"
• This provides better control and isolation for session-specific sync behavior

Example

If you have:

sync:
  symbols:
    - BTCUSDT
    - ETHUSDT
    - binance:BNBUSDT

Before: The binance session would sync BTCUSDT, ETHUSDT, and BNBUSDT
After: The binance session will sync only BNBUSDT, while other sessions sync BTCUSDT and ETHUSDT