proxymap, various: distinguish between different protocols

Previously, we were registering TCP and UDP connections in the same map,
which could result in erroneously removing a mapping if one of the two
connections completes while the other one is still active.

Add a "proto string" argument to these functions to avoid this.
Additionally, take the "proto" argument in LocalAPI, and plumb that
through from the CLI and add a new LocalClient method.

Updates tailscale/corp#20600

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I35d5efaefdfbf4721e315b8ca123f0c8af9125fb

ipn/ipnlocal/peerapi.go

@@ -187,7 +187,7 @@ func (pln *peerAPIListener) serve() {
 
 func (pln *peerAPIListener) ServeConn(src netip.AddrPort, c net.Conn) {
 	logf := pln.lb.logf
-	peerNode, peerUser, ok := pln.lb.WhoIs(src)
+	peerNode, peerUser, ok := pln.lb.WhoIs("tcp", src)
 	if !ok {
 		logf("peerapi: unknown peer %v", src)
 		c.Close()