Support multiple module annotations per atom

Bug: 150864291
Test: m stats-log-api-gen-test &&
out/host/linux-x86/nativetest/stats-log-api-gen-test/stats-log-api-gen-test

Change-Id: Ibf8869078c6f1eae13e687f0196d6ed91ec35c64
diff --git a/stats/atom_field_options.proto b/stats/atom_field_options.proto
index 9c875ba..40a24dc 100644
--- a/stats/atom_field_options.proto
+++ b/stats/atom_field_options.proto
@@ -116,5 +116,5 @@
 
     optional bool allow_from_any_uid = 50003 [default = false];
 
-    optional string module = 50004;
+    repeated string module = 50004;
 }