Make __hello_only__ a frozen-only alias of __hello__ (#7160)

Remove __hello_only__.py source file and its symlink. Register
__hello_only__ as a frozen module alias reusing __hello__ bytecode,
matching the behavior where origname is None (no source file).

Lib/__hello_only__.py

@@ -1,2 +0,0 @@
-initialized = True
-print("Hello world!")

crates/vm/Lib/python_builtins/__hello_only__.py

@@ -1 +0,0 @@
-../../../../Lib/__hello_only__.py

crates/vm/src/vm/interpreter.rs

@@ -491,6 +491,13 @@ fn core_frozen_inits() -> impl Iterator<Item = (&'static str, FrozenModule)> {
                 package: false,
             },
         ));
+        entries.push((
+            "__hello_only__",
+            FrozenModule {
+                code: hello_code,
+                package: false,
+            },
+        ));
     }
     if let Some(code) = entries
         .iter()