Simplify arguments of flux trace command

It now accepts arguments in the forms <resource>/<name>
and <resource> <name> instead of requiring api version and
kind as flags.

Signed-off-by: Jakob Schrettenbrunner <jakob.schrettenbrunner@telekom.de>

cmd/flux/trace_test.go

@@ -10,7 +10,7 @@ import (
 func TestTraceNoArgs(t *testing.T) {
 	cmd := cmdTestCase{
 		args:   "trace",
-		assert: assertError("object name is required"),
+		assert: assertError("either `<resource>/<name>` or `<resource> <name>` is required as an argument"),
 	}
 	cmd.runTestCmd(t)
 }