feat(workflows): add "attribute action" action

This action lets users perform several actions on threads, such as
(un)lock, (un)set as trending, (un)pin, set as non-issue, obsolete, etc.

The action selector shows the action with the codename it has in the
Protobuf enum. We will show a friendly string when we localize the
feature.

Bug: twpowertools:74

Change-Id: I95f9f1904ffe559c92a786cbdb327613c8ca32ca
diff --git a/src/workflows/proto/main.proto b/src/workflows/proto/main.proto
index 660be5e..dd10682 100644
--- a/src/workflows/proto/main.proto
+++ b/src/workflows/proto/main.proto
@@ -64,6 +64,11 @@
       AA_UNSET_TRENDING = 9;
       AA_SET_ISSUE_RESOLVED = 10;
       AA_UNSET_ISSUE_RESOLVED = 11;
+      AA_SOFT_LOCK = 12;
+      AA_UNSOFT_LOCK = 13;
+      AA_EXCLUDE_FROM_GOLDEN = 14;
+      AA_UNEXCLUDE_FROM_GOLDEN = 15;
+      AA_INCLUDE_IN_GOLDEN = 16;
     }
     AttributeAction attribute_action = 1;
   }