Fix tests of refinalization after optimization of selects (#7595)

According to their comments, these tests purported to show that
refinalize was run after optimizing a select to a single arm with a more
refined type. However,the tests were flawed because the select arms had
the same type, meaning the parsed select node did not have a less
refined type than the arms. Fix this by giving the arms different types.
Use a block to directly show that refinalization occurred instead of the
cast that was there previously.

Author: tlively