GID Map processor for single experiments with multiple platforms

### Context

Discussing with @jaclyn-taroni what we should do with #210 for milestone keytar kurt.

### Problem or idea

We should use our simple no-op processor (with gene ID mapping) on these cases for our June 1 goal.

### Solution or next step

We need to implement such a processor and apply it to any datasets that have multiple platforms and are not a superseries. Depends on #186

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Review issues #186 and #210 first to understand the dependency and the intended handling of these experiments. Identify the existing simple no-op processor and the dataset-selection entry point, then verify that the processor is applied to datasets with multiple platforms that are not superseries.

Written by the indexing model from the issue text.