Challenge modal optimization - remove unnecessary API call - partial fix for #9371 (#9546)

* Attempt to use party data from the store rather than always fetching it from the API

* Move init code to shown() to prevent unnecessary network requests

* Use store party data in getGroup action if possible to save an API call

* Use store data rather than API call for party in challengeModal; remove unnecessary code in guilds:getGroup action

* Create party:getParty action and employ it in Group and ChallengeModal

* Use store instead of action return for party data

* Change how party data is stored

website/client/components/groups/questDetailsModal.vue

@@ -173,7 +173,7 @@ export default {
   computed: {
     ...mapState({
       user: 'user.data',
-      partyMembers: 'party.members.data',
+      partyMembers: 'partyMembers.data',
     }),
     questData () {
       return quests.quests[this.group.quest.key];