fix reading gtc arrays when planes are stored in different adios blocks

@dpugmire This fixes the issue I emailed you about. It turns out that Kshitij's data had each plane written to a different ADIOS block, while our test data set has all planes being written to a single block. This is fine if you're not doing setting a BLOCK_SELECTION in the Fides metadata, but ParaView does this to split data across ranks. We handled things similarly in XGC where Fides blocks don't end up being the same thing as ADIOS blocks.