Multiplex Controller (Bypass connection-based speed limit)

[gfw-killer]

Is your feature request related to a problem? Please describe.
Hy2 makes only 1 multiplexed connection for all client's sub-connections, in the cases that speed of each connection is limited, performance of Hy2 is also limited.

Describe the solution you'd like
Hysteria2 can add option to make a connection pool and do a load-balance, or make a new connection when the last connection has N sub-connections.

Describe alternatives you've considered
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Additional context
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[haruue]

Using multiple QUIC connections can break the "brutal" congestion control. And I don't think using a connection pool will help if port-hopping doesn't work in your situation.

[gfw-killer]

Brutal has customizable bandwidth, it should be compatible with a connection pool
If internet max speed is 4MB and connection speed limit is 1MB, Hy2 can make 4 connections each 1MB bandwidth
and if there be a mux setting (open a new connection for each N sub-connections), BBR can handle it

[APT-ZERO]

If quic-go support Multipath, it may be possible to create multiple proxy connections to carry a single connection, or even combine multiple internet connections to increase internet speed