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_gio_mime.yaml

@@ -11,7 +11,8 @@
   output:
     handler: google-chrome.desktop
     changed: true
-  run_command_calls:
+  mocks:
+    run_command:
     - command: [/testbin/gio, mime, x-scheme-handler/http]
       environ: &env-def {environ_update: {LANGUAGE: C, LC_ALL: C}, check_rc: true}
       rc: 0
@@ -32,7 +33,8 @@
     changed: true
   flags:
     skip: test helper does not support check mode yet
-  run_command_calls:
+  mocks:
+    run_command:
     - command: [/testbin/gio, mime, x-scheme-handler/http]
       environ: *env-def
       rc: 0
@@ -51,7 +53,8 @@
   output:
     handler: google-chrome.desktop
     changed: false
-  run_command_calls:
+  mocks:
+    run_command:
     - command: [/testbin/gio, mime, x-scheme-handler/http]
       environ: *env-def
       rc: 0