TEST: Clarify test_restrictions a bit.
TEST: Clarify test_restrictions a bit.

- Use parameter_space instead of `parameterized.expand`.
- Use a timedelta instead of concatenating strings.
- Use a (possibly no-op) scramble function instead of reordering list
  literals.
- Use `freeze_dt, unfreeze_dt, re_freeze_dt` instead of `dts[n]`.
- Rename `assert_vectorized_results` to `assert_all_restrictions`.

florentchandelier/zipline,alphaBenj/zipline,enigmampc/catalyst,quantopian/zipline,quantopian/zipline,florentchandelier/zipline,bartosh/zipline,Scapogo/zipline,alphaBenj/zipline,Scapogo/zipline,bartosh/zipline,humdings/zipline,humdings/zipline,enigmampc/catalyst