Get rid of LifecycleMixin

It's poorly documented but there used to be `@hook:mounted/...` in Vue 2
already and now there is `@vue:mounted/...` let's use that instead of our
own custom lifecycle mixin

packages/web-app-files/src/components/SideBar/SideBar.vue

@@ -13,8 +13,8 @@
     :is-header-compact="isSingleResource"
     v-bind="$attrs"
     data-custom-key-bindings="true"
-    @beforeUnmount="destroySideBar"
-    @mounted="focusSideBar"
+    @vue:beforeUnmount="destroySideBar"
+    @vue:mounted="focusSideBar"
     @fileChanged="focusSideBar"
     @selectPanel="setActiveSideBarPanel"
     @close="closeSideBar"

packages/web-runtime/src/App.vue

@@ -32,8 +32,8 @@
       @input="modal.onInput"
       @checkbox-changed="modal.onCheckboxValueChanged"
       @confirm-secondary="modal.onConfirmSecondary"
-      @mounted="focusModal"
-      @beforeUnmount="focusModal"
+      @vue:mounted="focusModal"
+      @vue:beforeUnmount="focusModal"
     >
       <template v-if="modal.customContent" #content>
         <div v-html="modal.customContent"></div>

packages/web-runtime/src/defaults/vue.js

@@ -3,7 +3,6 @@ import Vue from 'vue'
 import WebPlugin from '../plugins/web'
 import Avatar from '../components/Avatar.vue'
 import focusMixin from '../mixins/focusMixin'
-import lifecycleMixin from '../mixins/lifecycleMixin'
 import VueEvents from 'vue-events'
 import VueScrollTo from 'vue-scrollto'
 import VueResize from 'vue-resize'
@@ -28,7 +27,6 @@ Vue.use(AsyncComputed)
 Vue.component('AvatarImage', Avatar)
 
 Vue.mixin(focusMixin)
-Vue.mixin(lifecycleMixin)
 
 // externalize Vue - this is not the Vue instance but the class
 window.Vue = Vue