Resolve ambiguity with apprise.plugins module namespace

While the namespace is physically made of modules, it has been amended
to be the namespace home for the corresponding notifier classes as well.

This turned out to confuse both humans and machines on various ends.

While it has apparently worked for a while, it croaks on Python 3.11
now, and is not considered to have been a good idea in general.

test/test_plugin_signal.py

@@ -29,8 +29,8 @@ from unittest import mock
 
 import pytest
 import requests
-from apprise import plugins
 from apprise import Apprise
+from apprise.plugins.NotifySignalAPI import NotifySignalAPI
 from helpers import AppriseURLTester
 from apprise import AppriseAttachment
 from apprise import NotifyType
@@ -67,7 +67,7 @@ apprise_url_tests = (
     }),
     ('signal://localhost/{}/123/'.format('1' * 11), {
         # invalid 'to' phone number
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # Notify will fail because it couldn't send to anyone
         'response': False,
         # Our expected url(privacy=True) startswith() response:
@@ -75,67 +75,67 @@ apprise_url_tests = (
     }),
     ('signal://localhost:8080/{}/'.format('1' * 11), {
         # one phone number will notify ourselves
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
 
     ('signal://localhost:8082/+{}/@group.abcd/'.format('2' * 11), {
         # a valid group
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # Our expected url(privacy=True) startswith() response:
         'privacy_url': 'signal://localhost:8082/+{}/@abcd'.format('2' * 11),
     }),
     ('signal://localhost:8080/+{}/group.abcd/'.format('1' * 11), {
         # another valid group (without @ symbol)
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # Our expected url(privacy=True) startswith() response:
         'privacy_url': 'signal://localhost:8080/+{}/@abcd'.format('1' * 11),
     }),
     ('signal://localhost:8080/?from={}&to={},{}'.format(
         '1' * 11, '2' * 11, '3' * 11), {
         # use get args to acomplish the same thing
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
     ('signal://localhost:8080/?from={}&to={},{},{}'.format(
         '1' * 11, '2' * 11, '3' * 11, '5' * 3), {
         # 2 good targets and one invalid one
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
     ('signal://localhost:8080/{}/{}/?from={}'.format(
         '1' * 11, '2' * 11, '3' * 11), {
         # If we have from= specified, then all elements take on the to= value
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
     ('signals://user@localhost/{}/{}'.format('1' * 11, '3' * 11), {
         # use get args to acomplish the same thing (use source instead of from)
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
     ('signals://user:password@localhost/{}/{}'.format('1' * 11, '3' * 11), {
         # use get args to acomplish the same thing (use source instead of from)
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
     }),
     ('signals://user:password@localhost/{}/{}'.format('1' * 11, '3' * 11), {
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # Test that a 201 response code is still accepted
         'requests_response_code': 201,
     }),
     ('signals://localhost/{}/{}/{}?batch=True'.format(
         '1' * 11, '3' * 11, '4' * 11), {
             # test batch mode
-            'instance': plugins.NotifySignalAPI,
+            'instance': NotifySignalAPI,
     }),
     ('signals://localhost/{}/{}/{}?status=True'.format(
         '1' * 11, '3' * 11, '4' * 11), {
             # test status switch
-            'instance': plugins.NotifySignalAPI,
+            'instance': NotifySignalAPI,
     }),
     ('signal://localhost/{}/{}'.format('1' * 11, '4' * 11), {
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # throw a bizzare code forcing us to fail to look it up
         'response': False,
         'requests_response_code': 999,
     }),
     ('signal://localhost/{}/{}'.format('1' * 11, '4' * 11), {
-        'instance': plugins.NotifySignalAPI,
+        'instance': NotifySignalAPI,
         # Throws a series of connection and transfer exceptions when this flag
         # is set and tests that we gracfully handle them
         'test_requests_exceptions': True,
@@ -175,7 +175,7 @@ def test_plugin_signal_edge_cases(mock_post, no_throttling):
 
     # No apikey specified
     with pytest.raises(TypeError):
-        plugins.NotifySignalAPI(source=None)
+        NotifySignalAPI(source=None)
 
     aobj = Apprise()
     assert aobj.add("signals://localhost:231/{}/{}".format(source, target))
@@ -321,7 +321,7 @@ def test_notify_signal_plugin_attachments(mock_post, no_throttling):
     obj = Apprise.instantiate(
         'signal://10.0.0.112:8080/+12512222222/+12513333333/'
         '12514444444?batch=no')
-    assert isinstance(obj, plugins.NotifySignalAPI)
+    assert isinstance(obj, NotifySignalAPI)
 
     # Test Valid Attachment
     path = os.path.join(TEST_VAR_DIR, 'apprise-test.gif')
@@ -364,7 +364,7 @@ def test_notify_signal_plugin_attachments(mock_post, no_throttling):
     obj = Apprise.instantiate(
         'signal://10.0.0.112:8080/+12512222222/+12513333333/'
         '12514444444?batch=yes')
-    assert isinstance(obj, plugins.NotifySignalAPI)
+    assert isinstance(obj, NotifySignalAPI)
 
     # Now send an attachment normally without issues
     mock_post.reset_mock()