gccrs: Remove class AST::InherentImplItem

gccrs: Remove class AST::InherentImplItem

gcc/rust/ChangeLog:

	* ast/rust-ast-full-decls.h
	(class InherentImplItem): Remove.
	* ast/rust-ast.h
	(class InherentImplItem): Remove.
	(class SingleASTNode):
	Store pointer to AssociatedItem instead of InherentImplItem.

	* ast/rust-ast.cc
	(SingleASTNode::SingleASTNode):
	Use clone_associated_item instead of clone_inherent_impl_item.
	(SingleASTNode::operator=): Likewise.

	* ast/rust-item.h
	(class InherentImpl):
	Use AssociatedItem rather than InherentImplItem.
	(class Function): Likewise.
	(class ConstantItem): Likewise.
	* ast/rust-macro.h
	(class MacroInvocation): Likewise.
	* expand/rust-expand-visitor.cc
	(ExpandVisitor::visit): Likewise.
	* parse/rust-parse-impl.h
	(Parser::parse_impl): Likewise.
	(Parser::parse_inherent_impl_item): Likewise.
	(Parser::parse_inherent_impl_function_or_method): Likewise.
	* parse/rust-parse.h
	(Parser::parse_inherent_impl_item): Likewise.
	(Parser::parse_inherent_impl_function_or_method): Likewise.

Signed-off-by: Owen Avery <powerboat9.gamer@gmail.com>