Running an experimental plugin with non experimental CLI should show a friendly message

[silvin-lubecki]

Description Running an experimental plugin with non experimental CLI should show a friendly message. The code seams to be here already, but something is short-circuiting it.

Steps to reproduce the issue:

Wrote some e2e tests in e2e/cli-plugins/run_test.go:

// TestPluginExperimentalWithNonExperimentalCLI tests when the plugin is labelled as experimental but
// not the CLI, which should print a message asking the user to activate experimental mode.
func TestPluginExperimentalWithNonExperimentalCLI(t *testing.T) {
	run, cfg, cleanup := prepare(t)
	defer cleanup()
	cfg.Experimental = "disabled"
	err := cfg.Save()
	assert.NilError(t, err)

	cmd := run("helloworld")
	cmd.Env = append(os.Environ(), "HELLO_EXPERIMENTAL=enabled")

	res := icmd.RunCmd(cmd)
	res.Assert(t, icmd.Expected{
		ExitCode: 1,
		Out:      icmd.None,
		Err:      "plugin candidate helloworld: requires experimental CLI",
	})
}

// TestPluginExperimentalWithExperimentalCLI tests when the plugin is labelled as experimental and
// the CLI too. The plugin should just work fine.
func TestPluginExperimentalWithExperimentalCLI(t *testing.T) {
	run, cfg, cleanup := prepare(t)
	defer cleanup()
	cfg.Experimental = "enabled"
	err := cfg.Save()
	assert.NilError(t, err)

	cmd := run("helloworld")
	cmd.Env = append(os.Environ(), "HELLO_EXPERIMENTAL=enabled")

	res := icmd.RunCmd(cmd)
	res.Assert(t, icmd.Expected{
		ExitCode: 0,
		Out:      "Hello World!",
		Err:      icmd.None,
	})
}

(paste your output here)

Additional environment details (AWS, VirtualBox, physical, etc.):

[thaJeztah]

/cc @tiborvass @andrewhsu