Convert TestReadProjection/TestSparkReadProjection to use Spark's InternalRow

[omalley]

In starting to look at working on Iceberg's schema evolution for ORC, the current test case is full of Avro's types/data structures. That doesn't work at all for ORC, because I don't have any desire to build those bindings.

Therefore, I'll make a version of TestSparkReadProjection that uses Iceberg's Schema and Spark's InternalRow. That will work with all three files formats.

Should I fork the current test classes? Or should I change the current test to be more generic?

[rdblue]

I'd say change the current test classes. The Avro module has its own TestReadProjection because it was easier to copy it than to mess with the build to have tests depend on other tests.