lang: core: Move template to golang namespace

I don't think this template function should be in any way authoritative,
so let's namespace it.

examples/lang/datetime4.mcl

@@ -1,4 +1,5 @@
 import "datetime"
+import "golang"
 import "sys"
 import "example"
 
@@ -6,5 +7,5 @@ $now = datetime.now()
 
 file "/tmp/mgmt-datetime" {
 	state => $const.res.file.state.exists,
-	content => template("Il est l'or Monseignor: {{ . }}\n", datetime.format($now, "15:04:05")),
+	content => golang.template("Il est l'or Monseignor: {{ . }}\n", datetime.format($now, "15:04:05")),
 }