SI-6387 Copy overriding accessor when expanding its name

When the compiler wants to make certain symbol accessible, it elevates the symbol 
with otherwise private visibility and expands its name to append the full name of 
containing class to avoid clashes.

In the rare cases when the accessor overrides the member in base class, such 
expanding either results in AbstractMethodError when the base method is abstract, or, 
even worse, can change the semantics of the program.

To avoid such issues, we clone the accessor symbol, clear its ACCESSOR flag and enter the symbol with an unchanged name.

This change only adds lost overridden methods, so the PR targets 2.10.x