feat: use tailnet v2 API for coordination (#11638)

This one is huge, and I'm sorry.

The problem is that once I change `tailnet.Conn` to start doing v2 behavior, I kind of have to change it everywhere, including in CoderSDK (CLI), the agent, wsproxy, and ServerTailnet.

There is still a bit more cleanup to do, and I need to add code so that when we lose connection to the Coordinator, we mark all peers as LOST, but that will be in a separate PR since this is big enough!

coderd/workspaceagents_test.go

@@ -535,7 +535,6 @@ func TestWorkspaceAgentTailnetDirectDisabled(t *testing.T) {
 	})
 	require.NoError(t, err)
 	defer conn.Close()
-	require.True(t, conn.BlockEndpoints())
 
 	require.True(t, conn.AwaitReachable(ctx))
 	_, p2p, _, err := conn.Ping(ctx)