Fix NoMethodError in MethodAttr#inspect for cache-loaded aliases

[SAY-5]

MethodAttr#inspect calls @is_alias_for.name directly, but for a method loaded from the ri cache @is_alias_for is still the unresolved [class, singleton, name] tuple, so calling inspect (e.g. p driver.stores.first.load_method("Array", "#append")) raises NoMethodError: undefined method 'name' for an instance of Array.

This mirrors the guard pretty_print already uses in the same file: use the resolved object's name when available, otherwise fall back to the method name from the tuple.

Closes #1737.