Convert some equivalence tests in test_*.py to assertions

fixes #8393
Merge pull request #8394 from skirpichev/8393-tests

Convert some equivalence tests in test_*.py to assertions
Relational.canonical simplifies Ge -> Le and Gt -> Lt

This is made part of Relational simplification and is
used in the equals method for Relationals.

The presence of Relationals in Booleans sent to equals
raises an error since that routine is not set up to handle
them.
quick