Remove Enum prefixes (#187)

Co-authored-by: nat <n@natn.me>
Co-authored-by: Tim Schmidt <w4rum@users.noreply.github.com>
Co-authored-by: Arun Babu Neelicattu <arun.neelicattu@gmail.com>

tests/inputs/enum/test_enum.py

@@ -1,4 +1,5 @@
 from tests.output_betterproto.enum import (
+    ArithmeticOperator,
     Choice,
     Test,
 )
@@ -102,3 +103,12 @@ def test_enum_mapped_on_parse():
 
     # bonus: defaults after empty init are also mapped
     assert Test().choice.name == Choice.ZERO.name
+
+
+def test_renamed_enum_members():
+    assert set(ArithmeticOperator.__members__) == {
+        "NONE",
+        "PLUS",
+        "MINUS",
+        "_0_PREFIXED",
+    }