TUN-8667: Add datagram v3 session manager

New session manager leverages similar functionality that was previously
provided with datagram v2, with the distinct difference that the sessions
are registered via QUIC Datagrams and unregistered via timeouts only; the
sessions will no longer attempt to unregister sessions remotely with the
edge service.

The Session Manager is shared across all QUIC connections that cloudflared
uses to connect to the edge (typically 4). This will help cloudflared be
able to monitor all sessions across the connections and help correlate
in the future if sessions migrate across connections.

The UDP payload size is still limited to 1280 bytes across all OS's. Any
UDP packet that provides a payload size of greater than 1280 will cause
cloudflared to report (as it currently does) a log error and drop the packet.

Closes TUN-8667

quic/v3/request.go

@@ -3,6 +3,7 @@ package v3
 import (
 	"encoding/binary"
 	"errors"
+	"fmt"
 )
 
 const (
@@ -37,6 +38,10 @@ func RequestIDFromSlice(data []byte) (RequestID, error) {
 	}, nil
 }
 
+func (id RequestID) String() string {
+	return fmt.Sprintf("%016x%016x", id.hi, id.lo)
+}
+
 // Compare returns an integer comparing two IPs.
 // The result will be 0 if id == id2, -1 if id < id2, and +1 if id > id2.
 // The definition of "less than" is the same as the [RequestID.Less] method.