Create tar.gz of legacy library with some un-migratable blocks

Using OLX, create a legacy library .tar.gz that includes:

1. An unsupported container type: itembank (aka Problem Bank)
2. Another unsupported container type: split_test (aka Content Experiment) nvm, this is redundant with (1)
3. A block which isn't installed, e.g. my_fake_block

   <my_fake_block url_name="fake">
        This XBlock type isn't installed anywhere, because I just invented it!
   </my_fake_block>
   

4. A block which is broken... but not in a way that should prevent its migration. e.g., an advanced problem with malformed CAPA.
5. As a control, a non-broken builtin block, like problem
6. As a control, a non-broken external block, like drag-and-drop-v2
7. As a control, a non-broken external advanced block, like edx-sga

Name the blocks so that it's obvious to the testers what the expected behavior of each one is.

Start by locating the OLX migration entry point and the test or fixture setup that consumes legacy libraries; no repository file or test is named in the issue. Build the requested tar.gz with clearly named cases for itembank, my_fake_block, malformed advanced problem, and the three controls, using the linked edx-sga vertical.xml example where relevant, then verify each migration outcome.