unit test helper: big revamp (#8894)

* initial commit

* multiple changes:

- TestCaseContext fixture no longer need to autouse=True
- Helper.from_module() allows extra param to specify yaml file
- test_django_check: adjusted .py and .yaml

* set fixtures per testcase

* set fixtures per testcase

* rollback to original state

* patch_ansible_module fixture

- now it works not only in parametrized functions but also directly with args

* tests/unit/plugins/modules/helper.py

- improved encapsulation, class Helper no longer knows details about test cases
- test functions no longer parametrized, that allows using test case fixtures per test function
- renamed 'context' to 'mock'

* enable Helper.from_list(), better param name 'ansible_module'

* adjusted test fiels to new helper

* remove unnecessary .license file

* fix bracket

* fix reference name

* Update tests/unit/plugins/modules/helper.py

Co-authored-by: Felix Fontein <felix@fontein.de>

* revert to parametrized test func instead of multiple funcs

---------

Co-authored-by: Felix Fontein <felix@fontein.de>

tests/unit/plugins/modules/test_django_check.yaml

@@ -7,7 +7,8 @@
 - id: success
   input:
     settings: whatever.settings
-  run_command_calls:
+  mocks:
+    run_command:
     - command: [/testbin/python, -m, django, check, --no-color, --settings=whatever.settings]
       environ: &env-def {environ_update: {LANGUAGE: C, LC_ALL: C}, check_rc: true}
       rc: 0
@@ -17,9 +18,10 @@
   input:
     settings: whatever.settings
     database:
-      - abc
-      - def
-  run_command_calls:
+    - abc
+    - def
+  mocks:
+    run_command:
     - command: [/testbin/python, -m, django, check, --no-color, --settings=whatever.settings, --database, abc, --database, def]
       environ: *env-def
       rc: 0