Make TestHelperImageRegistry not need real prebuilt images
What does this MR do?
Added code to create a bogus temp file in TestLocalHelperImage
so that the production code sees something there and tries to import it.
Why was this MR needed?
Otherwise we'd need to make the unit test
job depend on the helper image
job - I guess the only reason that these tests are working nowadays is because the machines running the tests have artifacts from previous builds
What's the best way to test this MR?
What are the relevant issue numbers?
Closes #27438 (closed)