PoC to use kpt functions as kustomize plugins

Closes [1]
In addition removes accidentally committed binary [2]

[1]
https://github.com/GoogleContainerTools/kpt/issues/646

[2]
1644fdd076 (diff-78873bc1f515e5cb644e68f0bcbaba23)

api/types/pluginconfig.go

@@ -29,4 +29,7 @@ type PluginConfig struct {
 
 	// BpLoadingOptions distinguishes builtin plugin behaviors.
 	BpLoadingOptions BuiltinPluginLoadingOptions
+
+	// FnpLoadingOpeions sets the way function-based plugin behaviors.
+	FnpLoadingOptions FnPluginLoadingOptions
 }

api/types/pluginrestrictions.go

@@ -41,3 +41,16 @@ const (
 	// to generate static code.
 	BploLoadFromFileSys
 )
+
+// FnPluginLoadingOptions set way functions-based pluing are restricted
+type FnPluginLoadingOptions struct {
+	// Allow to run executables
+	EnableExec         bool
+	// Allow to run starlark
+	EnableStar         bool
+	// Allow container access to network
+	Network            bool
+	NetworkName        string
+	// list of mounts
+	Mounts             []string
+}