feat: Replace alertMixin usage with useAlert (#9793)

# Pull Request Template

## Description

This PR will replace the usage of `alertMixin` from the code base with
the `useAlert` composable.

Fixes
https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert

## Type of change

- [x] Breaking change (fix or feature that would cause existing
functionality not to work as expected)

## How Has This Been Tested?

Please refer this issue description

https://linear.app/chatwoot/issue/CW-3462/replace-alertmixin-usage-with-usealert


## Checklist:

- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [ ] I have commented on my code, particularly in hard-to-understand
areas
- [ ] I have made corresponding changes to the documentation
- [x] My changes generate no new warnings
- [x] I have added tests that prove my fix is effective or that my
feature works
- [x] New and existing unit tests pass locally with my changes
- [ ] Any dependent changes have been merged and published in downstream
modules

---------

Co-authored-by: Sojan Jose <sojan@pepalo.com>

app/javascript/dashboard/modules/conversations/components/MessageContextMenu.vue

@@ -104,7 +104,7 @@
   </div>
 </template>
 <script>
-import alertMixin from 'shared/mixins/alertMixin';
+import { useAlert } from 'dashboard/composables';
 import { mapGetters } from 'vuex';
 import messageFormatterMixin from 'shared/mixins/messageFormatterMixin';
 import AddCannedModal from 'dashboard/routes/dashboard/settings/canned/AddCanned.vue';
@@ -123,7 +123,7 @@ export default {
     TranslateModal,
     MenuItem,
   },
-  mixins: [alertMixin, messageFormatterMixin],
+  mixins: [messageFormatterMixin],
   props: {
     message: {
       type: Object,
@@ -183,12 +183,12 @@ export default {
       await copyTextToClipboard(
         `${fullConversationURL}?messageId=${this.messageId}`
       );
-      this.showAlert(this.$t('CONVERSATION.CONTEXT_MENU.LINK_COPIED'));
+      useAlert(this.$t('CONVERSATION.CONTEXT_MENU.LINK_COPIED'));
       this.handleClose();
     },
     async handleCopy() {
       await copyTextToClipboard(this.plainTextContent);
-      this.showAlert(this.$t('CONTACT_PANEL.COPY_SUCCESSFUL'));
+      useAlert(this.$t('CONTACT_PANEL.COPY_SUCCESSFUL'));
       this.handleClose();
     },
     showCannedResponseModal() {
@@ -233,10 +233,10 @@ export default {
           conversationId: this.conversationId,
           messageId: this.messageId,
         });
-        this.showAlert(this.$t('CONVERSATION.SUCCESS_DELETE_MESSAGE'));
+        useAlert(this.$t('CONVERSATION.SUCCESS_DELETE_MESSAGE'));
         this.handleClose();
       } catch (error) {
-        this.showAlert(this.$t('CONVERSATION.FAIL_DELETE_MESSSAGE'));
+        useAlert(this.$t('CONVERSATION.FAIL_DELETE_MESSSAGE'));
       }
     },
     closeDeleteModal() {