i18n, vue-router and vuex upgrade

1. Configuration of i18n legacy as false.
2. Translation function t is called using the useI18n.
3. Used the i18n.global.t() function from i18n instead of this.$t()
4. Event bus error that occurred during logout.
5. Implemented vue-router 4.4.0 and vuex upgrade to 4.1.0

Change-Id: I9464d82c76dcc1445ce271983ea3ab9d7b03d265
Signed-off-by: Surya Venkatesan <suryav@ami.com>
diff --git a/src/components/Global/ButtonBackToTop.vue b/src/components/Global/ButtonBackToTop.vue
index 3ceb691..f8d8b88 100644
--- a/src/components/Global/ButtonBackToTop.vue
+++ b/src/components/Global/ButtonBackToTop.vue
@@ -16,12 +16,14 @@
 import UpToTop24 from '@carbon/icons-vue/es/up-to-top/24';
 
 import { debounce } from 'lodash';
+import { useI18n } from 'vue-i18n';
 
 export default {
   name: 'BackToTop',
   components: { IconUpToTop: UpToTop24 },
   data() {
     return {
+      $t: useI18n().t,
       showButton: false,
     };
   },