Only show matching hashtags as suggests

The current behavior is to show all hashtags from changes that has one
hashtag that matches input. For a server that has wide use of hashtags
this is less helpful since a majority of the suggested hashtags aren't
matching the input.
Filter the array of existing hashtags for those matching the input.

Solves: bug 344608194
Change-Id: I7d75184594e925890860c84c156aee86eb782a08
Release-Notes: Only suggest matching hashtags.
diff --git a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
index b7851a6..7d35629 100644
--- a/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
+++ b/polygerrit-ui/app/elements/change/gr-change-metadata/gr-change-metadata.ts
@@ -1156,6 +1156,7 @@
           .flatMap(change => change.hashtags ?? [])
           .filter(isDefined)
           .filter(unique)
+          .filter(hashtag => hashtag.includes(input))
           .map(hashtag => {
             return {name: hashtag, value: hashtag};
           })