Create test version of NBAtlas cell type metadata

[sjspielman]

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Part of #1151

Describe the goals of the changes to the analysis module.

We have received cell type metadata from NBAtlas authors to use as part of the cell-type-neuroblastoma-04 module. For now, we would like to make a test version of this metadata which we can use for CI. This should be a text file with a list of cell IDs that should be considered tumor. We'll keep this small for use in CI!

Note that these IDs will also need to play well with the subsetted NBAtlas we're creating in this PR for testing: #1173

What will your pull request contain?

Text file with randomly-selected NBAtlas ids to consider tumor in testing

Will you require additional software beyond what is already in the analysis module?

No

Will you require different computational resources beyond what the analysis module already uses?

No

If known, when do you expect to file the pull request?

This sprint