Partitioned tables migrated to Iceberg aren't cached in LLAP

Files of migrated partitioned tables don't contain partition values, however Iceberg's read schema has them. The difference between this read schema and file schema is considered an unsupported schema evolution by LlapRecordReader so it bails out before starting to read.

We should remove identity partition column names from the read the schema, if we find that it's a not an Iceberg-written (so is migrated) file.