Fix SOCKS5 UDP proxies not working with Bedrock Edition

[Lenni0451]

This pull request refactors how proxies are injected into Netty channels, specifically improving support for Bedrock connections and clarifying the API for adding proxies. The main change is that the addProxy method now takes a Channel instead of a ChannelPipeline, allowing for more precise handling of Bedrock (RakNet) channels and better error reporting.

Netty proxy injection improvements:

• Changed the addProxy method in NettyHelper to accept a Channel instead of a ChannelPipeline, and updated all usages accordingly. This enables the method to access both the pipeline and channel-specific features. [1] [2]
• Improved Bedrock (RakNet) proxy handling: when using a SOCKS5 proxy with a Bedrock connection, the code now checks that the channel is a RakClientChannel and injects the handler into the RakNet pipeline. If the channel is not a RakClientChannel, an informative exception is thrown.
• Updated imports in NettyHelper.java to support the new channel type checks and handler injection.