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_kumulos.py

@@ -24,7 +24,8 @@
 # THE SOFTWARE.
 import pytest
 import requests
-from apprise import plugins
+
+from apprise.plugins.NotifyKumulos import NotifyKumulos
 from helpers import AppriseURLTester
 
 # Disable logging for a cleaner testing output
@@ -53,13 +54,13 @@ apprise_url_tests = (
     }),
     ('kumulos://{}/{}/'.format(UUID4, 'w' * 36), {
         # Everything is okay
-        'instance': plugins.NotifyKumulos,
+        'instance': NotifyKumulos,
 
         # Our expected url(privacy=True) startswith() response:
         'privacy_url': 'kumulos://8...2/w...w/',
     }),
     ('kumulos://{}/{}/'.format(UUID4, 'x' * 36), {
-        'instance': plugins.NotifyKumulos,
+        'instance': NotifyKumulos,
         # force a failure
         'response': False,
         'requests_response_code': requests.codes.internal_server_error,
@@ -68,7 +69,7 @@ apprise_url_tests = (
         'privacy_url': 'kumulos://8...2/x...x/',
     }),
     ('kumulos://{}/{}/'.format(UUID4, 'y' * 36), {
-        'instance': plugins.NotifyKumulos,
+        'instance': NotifyKumulos,
         # throw a bizzare code forcing us to fail to look it up
         'response': False,
         'requests_response_code': 999,
@@ -77,7 +78,7 @@ apprise_url_tests = (
         'privacy_url': 'kumulos://8...2/y...y/',
     }),
     ('kumulos://{}/{}/'.format(UUID4, 'z' * 36), {
-        'instance': plugins.NotifyKumulos,
+        'instance': NotifyKumulos,
         # Throws a series of connection and transfer exceptions when this flag
         # is set and tests that we gracfully handle them
         'test_requests_exceptions': True,
@@ -103,12 +104,12 @@ def test_plugin_kumulos_edge_cases(no_throttling):
 
     # Invalid API Key
     with pytest.raises(TypeError):
-        plugins.NotifyKumulos(None, None)
+        NotifyKumulos(None, None)
     with pytest.raises(TypeError):
-        plugins.NotifyKumulos("     ", None)
+        NotifyKumulos("     ", None)
 
     # Invalid Server Key
     with pytest.raises(TypeError):
-        plugins.NotifyKumulos("abcd", None)
+        NotifyKumulos("abcd", None)
     with pytest.raises(TypeError):
-        plugins.NotifyKumulos("abcd", "       ")
+        NotifyKumulos("abcd", "       ")