CDK-456: Fix assumption in HBase avro util and tests.

The tests previously assumed that the key schema field names matched the
original field names. Now that the key fields are created based on the
partition strategy, this isn't possible because the source fields can be
used multiple times. The fix is to look up the correct source field name
using the partition strategy.

This also fixes tests that assumed the names matched by adding the
matching names explicitly in the partition strategy. This is allowed for
HBase, but was broken because FieldPartitioner itself enforced that
source and partition names had to be different. This removes that
restriction and adds a test to make sure it is properly enforced for
Hive tables (non-Hive HDFS produces a warning). The enforcement was
already implemented in the Compatibility class, it just wasn't used
because FieldPartitioner was doing it.