Fix two tiny issues with autocompletion logging

- Do not report COMMENT_COMPLETION_SAVE_DRAFT, if no hint was accepted
- Add `hasDraftChanged` to COMMENT_COMPLETION_SUGGESTION_FETCHED

Release-Notes: skip
Change-Id: Ib20f37f33f07da4bde4e7951171c9f7e9a3ee3a8
diff --git a/polygerrit-ui/app/utils/autocomplete-cache.ts b/polygerrit-ui/app/utils/autocomplete-cache.ts
index c8077ab..b1dba44 100644
--- a/polygerrit-ui/app/utils/autocomplete-cache.ts
+++ b/polygerrit-ui/app/utils/autocomplete-cache.ts
@@ -24,6 +24,8 @@
   acceptedSuggestionsCount?: number;
   totalAcceptedCharacters?: number;
   savedDraftLength?: number;
+
+  hasDraftChanged?: boolean;
 }
 
 /**