[Generator] Always put expression body on a new line

generators/builtins/primitives/builders.kt

@@ -359,12 +359,11 @@ internal class MethodBuilder : AnnotatedAndDocumented(), PrimitiveBuilder {
 
     fun noBody() { body = null }
 
-    fun String.addAsSingleLineBody(bodyOnNewLine: Boolean = false) {
-        val skip = if (bodyOnNewLine) "$END_LINE    " else " "
-        body = " =$skip$this"
+    fun String.setAsExpressionBody() {
+        body = " =$END_LINE    $this"
     }
 
-    fun String.addAsMultiLineBody() {
+    fun String.setAsBlockBody() {
         body = " {$END_LINE${this.shift()}$END_LINE}"
     }
 }