Overcome Name comparison hurdles

[som-snytt]

Fixes #19274

When checking for conflicting members, track visited members by name.toString.
When checking for matching members, compare "target names" as simple names.

[som-snytt]

The github issue number autocomplete has gone from mostly useless to quite glitchy for me.

[som-snytt]

Edit: that tweak compares apples and oranges.

[som-snytt]

What is the behavior when the other method is from a superclass from the class path? Is its name also simple.

[som-snytt]

Is this just to defend against people using identifiers with dollars that happen to collide? Maybe this is too expensive to support, as it expensive in the happy path. Is it OK because name.toString is computed just once and is required eventually anyway? In that case, it should compare toString and not toSimpleName. (The hypothesis was that preferring comparisons with simple names would be cheaper on average, but that is untested. That is, toSimpleName is a no-op for simple names.)

[som-snytt]

The CB a error is the izumi-reflect example. The double definition is detected now.