Issue #3492930: Add ActivityAnswer plugin

...orm_display.lms_activity._bundle_placeholder_.default.yml

...iew_display.lms_activity._bundle_placeholder_.default.yml

....lms_activity._bundle_placeholder_.field_xapi_package.yml

...er/xapi/field.storage.lms_activity.field_xapi_package.yml

modules/lms_xapi_activity/lms_xapi_activity.info.yml

modules/lms_xapi_activity/lms_xapi_activity.services.yml

modules/lms_xapi_activity/src/ActivityXapiIdGenerator.php

modules/lms_xapi_activity/src/Plugin/ActivityAnswer/Xapi.php

modules/lms_xapi_lesson/lms_xapi_lesson.info.yml

src/Form/LmsXapiSettingsForm.php

tests/src/FunctionalJavascript/LmsXapiTest.php