build: Move the pylint_django_settings plugin.

When it was located at the root of the project, it was sometimes not
getting loaded correctly since the root of the project is not a python
module, and producing the following error:

```
Command line or configuration file:1:0: E0013: Plugin 'pylint_django_settings' is impossible to load, is it installed ? ('No module named 'pylint_django_settings'') (bad-plugin-value)
```

This led all the pylint tests to fail.

This started happening more as we updated other dependencies via make
upgrade for some reason and led to inconsistent builds.  The move should
hopefully make the loading reliable and consistent.

Author: feanil

.editorconfig

@@ -64,7 +64,7 @@
 # SERIOUSLY.
 #
 # ------------------------------
-# Generated by edx-lint version: 5.3.0
+# Generated by edx-lint version: 5.6.0
 # ------------------------------
 [*]
 end_of_line = lf
@@ -97,4 +97,4 @@ max_line_length = 72
 [*.rst]
 max_line_length = 79
 
-# eecef7d3f7f334de2348fe1b4b0b48d605f7dcab
+# 3eb1e01bd9ba6cdf1e5d0a493581c4ea14404b67

openedx/core/tests/pylint_django_settings/__init__.py

@@ -0,0 +1 @@
+from .plugin import register, load_configuration

pylint_django_settings.py …e/tests/pylint_django_settings/plugin.pypylint_django_settings.py renamed to openedx/core/tests/pylint_django_settings/plugin.py pylint_django_settings.py renamed to openedx/core/tests/pylint_django_settings/plugin.py

@@ -64,12 +64,12 @@
 # SERIOUSLY.
 #
 # ------------------------------
-# Generated by edx-lint version: 5.4.1
+# Generated by edx-lint version: 5.6.0
 # ------------------------------
 [MASTER]
 ignore = ,.git,.tox,migrations,node_modules,.pycharm_helpers
 persistent = yes
-load-plugins = edx_lint.pylint,pylint_django_settings,pylint_django,pylint_celery,pylint_pytest
+load-plugins = edx_lint.pylint,openedx.core.tests.pylint_django_settings,pylint_django,pylint_celery,pylint_pytest
 
 [MESSAGES CONTROL]
 enable = 
@@ -414,4 +414,4 @@ int-import-graph =
 [EXCEPTIONS]
 overgeneral-exceptions = builtins.Exception
 
-# 5aea7d7fb264005eb373099c856a54cdfa4f311c
+# d6e4348dec0a8eb2752fc4fe02315286c298aeff

pylintrc

@@ -1,7 +1,7 @@
 # pylintrc tweaks for use with edx_lint.
 [MASTER]
 ignore+ = ,.git,.tox,migrations,node_modules,.pycharm_helpers
-load-plugins = edx_lint.pylint,pylint_django_settings,pylint_django,pylint_celery,pylint_pytest
+load-plugins = edx_lint.pylint,openedx.core.tests.pylint_django_settings,pylint_django,pylint_celery,pylint_pytest
 
 [MESSAGES CONTROL]
 disable+ =