Documented v2_runner_on_failed method in Callback class

[garciart]

SUMMARY

Added type declarations and a docstring to the v2_runner_on_failed method of the Callback class to explain the purpose of the method and the parameters that the method will accept. The docstring also provides additional information for developers who want to use the method in custom callback plugins. This PR incorporates feedback from @bcoca and @webknjaz.

ISSUE TYPE

• Docs Pull Request

ADDITIONAL INFORMATION

This change does not alter the method's output. A block-rescue play using an ansible.builtin.fail module ran with no issues. All tests in test.units.plugins.callback.test_callback passed

$ python3 -m unittest --verbose --buffer test.units.plugins.callback.test_callback
test_display (test.units.plugins.callback.test_callback.TestCallback) ... ok
test_display_verbose (test.units.plugins.callback.test_callback.TestCallback) ... ok
test_host_label (test.units.plugins.callback.test_callback.TestCallback) ... ok
test_host_label_delegated (test.units.plugins.callback.test_callback.TestCallback) ... ok
test_init (test.units.plugins.callback.test_callback.TestCallback) ... ok
test_clear_file (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_diff_after_none (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_diff_before_none (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_diff_dicts (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_difflist (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_new_file (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_no_trailing_newline_after (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_no_trailing_newline_before (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_no_trailing_newline_both (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_no_trailing_newline_both_with_some_changes (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_simple_diff (test.units.plugins.callback.test_callback.TestCallbackDiff) ... ok
test_are_methods (test.units.plugins.callback.test_callback.TestCallbackOnMethods) ... ok
test_on_any (test.units.plugins.callback.test_callback.TestCallbackOnMethods) ... ok
test_clean_results (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok
test_clean_results_debug_task (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok
test_clean_results_debug_task_empty_results (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok
test_clean_results_debug_task_no_invocation (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok
test_get_item_label (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok
test_get_item_label_no_log (test.units.plugins.callback.test_callback.TestCallbackResults) ... ok

----------------------------------------------------------------------
Ran 24 tests in 0.003s

OK