[Chapel Merge] CG: Issue user errors upon CG innerCopy

Branch: refs/heads/master
Revision: fb32253
Author: vasslitvinov
Log Message:

Merge pull request #17369 from vasslitvinov/cg-dont-copyInner

CG: Issue user errors upon CG innerCopy

Currently copyInner() is not implemented properly
for InterfaceSymbol and ImplementsStmt because
the existing implementations do not handle
the non-AST data structures that these nodes store.
To prevent user surprises, issue user errors
if these methods are invoked.

None of the existing tests bump into these errors.

I am not adding any tests for these error messages
because this is not a desired behavior that we want to preserve.

Discussed with @mppf

Modified Files:
M compiler/AST/interfaces.cpp

Compare: https://github.com/chapel-lang/chapel/compare/8a250877907c...fb322538a5f2