GC pressure during ORC StringDictionary writes

When ORC string dictionary writes data out, it suffers from bad GC performance due to a few allocations in-loop.

The conversions are as follows

StringTreeWriter::getStringValue() causes 2 conversions

LazyString -> Text (LazyString::getWritableObject)
Text -> String (LazyStringObjectInspector::getPrimitiveJavaObject)

Then StringRedBlackTree::add() does one conversion

String -> Text

This causes some GC pressure with un-necessary String and byte[] array allocations.