gccrs: dump: Replace ast dump internals

gccrs: dump: Replace ast dump internals

Replace ast dump visitor with call to token collector.

gcc/rust/ChangeLog:

	* ast/rust-ast-collector.cc (TokenCollector::visit): Add a visit
	function for visitable abstract class so we can call a dump on
	any visitable item.
	* ast/rust-ast-collector.h: Add new visit function prototype.
	* ast/rust-ast-dump.cc (Dump::go): Add call to process function.
	(Dump::visit): Remove functions.
	(Dump::visit_items_joined_by_separator): Likewise.
	(Dump::visit_as_line): Likewise.
	(Dump::visit_items_as_lines): Likewise.
	(Dump::visit_items_as_block): Likewise.
	(Dump::visit_function_common): Likewise.
	(get_delimiters): Likewise.
	(Dump::debug): Update with call to tokencollector.
	* ast/rust-ast-dump.h (RUST_AST_DUMP_H): Move include
	directives.
	(class Dump): Remove multiple prototypes and add generic process
	function.

Signed-off-by: Pierre-Emmanuel Patry <pierre-emmanuel.patry@embecosm.com>