Parameterize many of the threshold tests (home-assistant#125521)

threshold: Parameterize many of the tests

This simplfies the structure of the basic threshold tests,
making it easier to subsequently update or add missing test cases.

Except for a few removals of an inconsistenly applied assertions on
`state.attributes["sensor_value"]`, there are no changes to the existing
tests intended. All previous tests are expected to run identically.

A few extra test cases for None are added.