[IMP] mail, *: move up model files

Move model definition files from `models/thing/thing.js` to
`models/thing.js` and remove the now empty intermediate directory.

Task-2759582
 * = calendar, crm_livechat, hr, im_livechat, mail_bot, sms, snailmail,
     website_livechat, website_slides

closes odoo/odoo#86464

Related: odoo/enterprise#25291
Signed-off-by: Alexandre Kühn (aku) <aku@odoo.com>

addons/snailmail/static/src/models/dialog.js

@@ -4,7 +4,7 @@ import { addFields, addRecordMethods, patchIdentifyingFields, patchRecordMethods
 import { one } from '@mail/model/model_field';
 import { clear, insertAndReplace, replace } from '@mail/model/model_field_command';
 // ensure that the model definition is loaded before the patch
-import '@mail/models/dialog/dialog';
+import '@mail/models/dialog';
 
 patchIdentifyingFields('Dialog', identifyingFields => {
     identifyingFields[0].push('messageViewOwnerAsSnailmailError');

addons/snailmail/static/src/models/message.js

@@ -2,7 +2,7 @@
 
 import { addRecordMethods } from '@mail/model/model_core';
 // ensure that the model definition is loaded before the patch
-import '@mail/models/message/message';
+import '@mail/models/message';
 
 addRecordMethods('Message', {
     /**

addons/snailmail/static/src/models/message_view.js

@@ -4,7 +4,7 @@ import { addFields, patchRecordMethods } from '@mail/model/model_core';
 import { one } from '@mail/model/model_field';
 import { insertAndReplace } from '@mail/model/model_field_command';
 // ensure that the model definition is loaded before the patch
-import '@mail/models/message_view/message_view';
+import '@mail/models/message_view';
 
 addFields('MessageView', {
     snailmailErrorDialog: one('Dialog', {

addons/snailmail/static/src/models/messaging.js

@@ -3,7 +3,7 @@
 import { addFields, addRecordMethods } from '@mail/model/model_core';
 import { attr } from '@mail/model/model_field';
 // ensure that the model definition is loaded before the patch
-import '@mail/models/messaging/messaging';
+import '@mail/models/messaging';
 
 addRecordMethods('Messaging', {
     async fetchSnailmailCreditsUrl() {

addons/snailmail/static/src/models/notification_group.js

@@ -2,7 +2,7 @@
 
 import { patchRecordMethods } from '@mail/model/model_core';
 // ensure that the model definition is loaded before the patch
-import '@mail/models/notification_group/notification_group';
+import '@mail/models/notification_group';
 
 patchRecordMethods('NotificationGroup', {
     /**