[SPARK-12058][STREAMING][KINESIS][TESTS] fix Kinesis python tests

Python tests require access to the `KinesisTestUtils` file. When this file exists under src/test, python can't access it, since it is not available in the assembly jar.

However, if we move KinesisTestUtils to src/main, we need to add the KinesisProducerLibrary as a dependency. In order to avoid this, I moved KinesisTestUtils to src/main, and extended it with ExtendedKinesisTestUtils which is under src/test that adds support for the KPL.

cc zsxwing tdas

Author: Burak Yavuz <brkyvz@gmail.com>

Closes #10050 from brkyvz/kinesis-py.