Use `assetHelper.withCleaner` Within `ApiGwCliBasicTests.scala` Tests

The tests within `incubator-openwhisk-cli/tests/src/test/scala/whisk/core/cli/testApiGwCliBasicTests.scala` tend to not use the `assetHelper` for several action/api tests. Instead, the action and/or api is cleaned up explicitly in each test's `finally` block via `action.delete`. This should be improved to use the `assetHelper` for more concise test code.

The other tests within this repo tend to use this `assetHelper` appropriately, but they all could use a look to make sure the usage is aligned.

Start by reading incubator-openwhisk-cli/tests/src/test/scala/whisk/core/cli/testApiGwCliBasicTests.scala and inspect how its action and API tests use assetHelper versus explicit finally-block cleanup. Align the relevant tests with the repository's existing assetHelper usage, then check the other tests for similar inconsistencies. Done means cleanup is concise and consistently handled through assetHelper.

Scritto dal modello di indicizzazione a partire dal testo della issue.