Migrate name prefix usage to new interface

Summary: This is a Hack-only change to migrate usage of the `edward-io.NamePrefix` annotation from the old to the new interface. This change is non-semantic (see: no changes to Hack generated code) and therefore should be safe to land

Reviewed By: rmakheja, odedblayer

Differential Revision: D113120520

fbshipit-source-id: b0a438f17fda5d0855b207cfe5b3e59d8df1a133

Author: a-lafrance

exactprint/tests/fbthrift-tests/php_hack_ns/src/module.thrift

@@ -40,12 +40,14 @@ union TestUnion {
   1: string string_value;
 }
 
-@hack.NamePrefix{prefix = "Prefixed", apply_on_getName = false}
+@hack.NamePrefix{prefix = "Prefixed"}
+@hack.LegacyOmitPrefixInNameString
 exception TestException {
   1: string message;
 }
 
-@hack.NamePrefix{prefix = "Double_", apply_on_getName = false}
+@hack.NamePrefix{prefix = "Double_"}
+@hack.LegacyOmitPrefixInNameString
 @hack.Name{name = "Prefixed_"}
 struct TestStruct {
   1: string str_value;