Refine logic for when to show "outdated votes" messages

In change 344058 the logic was changed such that *all* patchset uploads
with outdated votes would be shown by default. This has led to an
unexpected amount of clutter in the Change Log.

Do not show such messages for WIP patchset uploads.

Only show the latest of such patchset uploads with outdated votes.

Change 344058 is completely reverted, because it seemed more appropriate
to implement the logic in `computeTag()` than in `computeIsImportant()`.

Release-Notes: skip
Google-Bug-Id: b/241597611
Change-Id: Id6eeecf1d0e50e6baf39438233740f1480fa611c
diff --git a/polygerrit-ui/app/constants/constants.ts b/polygerrit-ui/app/constants/constants.ts
index c8ce09e..503c35a 100644
--- a/polygerrit-ui/app/constants/constants.ts
+++ b/polygerrit-ui/app/constants/constants.ts
@@ -68,6 +68,7 @@
 export enum MessageTag {
   TAG_DELETE_REVIEWER = 'autogenerated:gerrit:deleteReviewer',
   TAG_NEW_PATCHSET = 'autogenerated:gerrit:newPatchSet',
+  TAG_NEW_PATCHSET_OUTDATED_VOTES = 'autogenerated:gerrit:newPatchSetOutdatedVotes',
   TAG_NEW_WIP_PATCHSET = 'autogenerated:gerrit:newWipPatchSet',
   TAG_REVIEWER_UPDATE = 'autogenerated:gerrit:reviewerUpdate',
   TAG_SET_PRIVATE = 'autogenerated:gerrit:setPrivate',