PYTHON-5514 Specific assertions for "is" and "is not None"

[sleepyStick]

(grouped them together because there wasn't a lot of each, but i can seperate the two into two different PRs if that's preferred)

self.assertTrue(x is y) -> self.assertIs(x, y)
self.assertTrue(x is not None) -> self.assertIsNotNone(x)

[aclark4life]

LGTM! The only minor issue (nit, even) I notice is that "better" is subjective and what's actually changing is the assertions, from general (True/False) to specific (Is/IsNot) and that is objectively better 😂

[sleepyStick]

LGTM! The only minor issue (nit, even) I notice is that "better" is subjective and what's actually changing is the assertions, from general (True/False) to specific (Is/IsNot) and that is objectively better 😂

Good point! thanks for the name change!