Add test coverage for #3857 : NullReferenceException issue when using SqlDataAdapter with Always Encrypted and UpdateBatchSize > 1

[apoorvdeshmukh]

We need to use the repro mentioned in #3716 for adding test coverage for fix introduced through #3857.
The earlier test coverage has identified some issues in existing always encrypted test cases which also need to be addressed while adding this test coverage.
Additionally this needs to be backported to release/6.1 and release/6.0.