Create WW retain schema integration test for all components

[chukarsten]

Per our discussion on #3310 , we wanted to create a similar retain_ww_schema style tests that copies def test_drop_rows_transformer_retain_ww_schema(): in evalml/tests/component_tests/test_drop_nan_rows_transformer.py but have them iterate over all the components.

Successful completion of this task is the removal of the drop rows transformer tests and the replacement of it with the generic retain_ww_schema style tests for all transformers within our integration tests (not unit tests?)