Follow-up testing for notnull-param-state

[RikkiGibson]

Consider making this test a [Theory] and using an argument to enumerate all the different constraint combinations where this is now valid.

Originally posted by @jaredpar in #46072 (comment)

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Consider adding a test here there is an override that removes the nullability annotation and calls through both the base and derived type and shows the outcome on the null state of the argument. Basically making sure we are considering the base and derived method annotation as appropriate.

I actually can't remember off hand if we look at the declaration method or the override when considering annotations hence I can't remember what the correct behavior is here. Hence a test 😄

Originally posted by @jaredpar in #46072 (comment)