## Summary
In order to make cloudflared behavior more predictable and
prevent an exhaustion of resources, we have decided to add
session limits that can be configured by the user. This first
commit introduces the session limiter and adds it to the UDP
handling path. For now the limiter is set to run only in
unlimited mode.
A new ICMPResponder interface is introduced to provide different
implementations of how the ICMP flows should return to the QUIC
connection muxer.
Improves usages of netip.AddrPort to leverage the embedded zone
field for IPv6 addresses.
Closes TUN-8640
The current supervisor serves the quic connection by performing all of the following in one method:
1. Dial QUIC edge connection
2. Initialize datagram muxer for UDP sessions and ICMP
3. Wrap all together in a single struct to serve the process loops
In an effort to better support modularity, each of these steps were broken out into their own separate methods that the supervisor will compose together to create the TunnelConnection and run its `Serve` method.
This also provides us with the capability to better interchange the functionality supported by the datagram session manager in the future with a new mechanism.
Closes TUN-8661
João "Pisco" Fernandes
Devin Carr