[MOV] (test_)mail: reorganize mail test tools files

Since a few time, test_mail holds tests linked to specific test models.
Generic testing of mail features are located in mail. Followup of fix done
in 12 and forward ported until odoo/odoo@b7af68590e

Also rename test_mass_mailing_server.py unit test file to test_mailing_server
to match current naming of files.

Task ID-2377974
Community PR odoo/odoo#61467

addons/mail/tests/__init__.py

@@ -5,5 +5,6 @@ from . import test_mail_channel
 from . import test_mail_channel_partner
 from . import test_mail_full_composer
 from . import test_mail_render
+from . import test_mail_tools
 from . import test_res_partner
 from . import test_update_notification

addons/mail/tests/test_mail_tools.py

@@ -1,12 +1,12 @@
 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 
-from odoo.addons.test_mail.tests.common import TestMailCommon, TestRecipients
+from odoo.addons.mail.tests.common import MailCommon
 from odoo.tests import tagged, users
 
 
 @tagged('mail_tools')
-class TestMailTools(TestMailCommon, TestRecipients):
+class TestMailTools(MailCommon):
 
     @classmethod
     def setUpClass(cls):

addons/test_mail/tests/__init__.py

@@ -11,7 +11,6 @@ from . import test_mail_mail
 from . import test_mail_gateway
 from . import test_mail_thread_internals
 from . import test_mail_template
-from . import test_mail_tools
 from . import test_message_management
 from . import test_message_post
 from . import test_message_track

addons/test_mass_mailing/tests/__init__.py

@@ -5,7 +5,7 @@ from . import test_blacklist
 from . import test_blacklist_behavior
 from . import test_blacklist_mixin
 from . import test_link_tracker
-from . import test_mailing_test
 from . import test_mailing
-from . import test_mass_mailing_server
+from . import test_mailing_server
+from . import test_mailing_test
 from . import test_performance