chore: remove middleware to request version and entitlement warnings (#12750)

This cleans up `root.go` a bit, adds tests for middleware HTTP transport
functions, and removes two HTTP requests we always always performed previously
when executing *any* client command.

It should improve CLI performance (especially for users with higher latency).

cli/root_test.go

@@ -253,7 +253,7 @@ func TestHandlersOK(t *testing.T) {
 	t.Parallel()
 
 	var root cli.RootCmd
-	cmd, err := root.Command(root.Core())
+	cmd, err := root.Command(root.CoreSubcommands())
 	require.NoError(t, err)
 
 	clitest.HandlersOK(t, cmd)