gccrs: Add dump configuration options, fix node exclusion

gccrs: Add dump configuration options, fix node exclusion

gcc/rust/ChangeLog:

	* ast/rust-ast-collector.cc (TokenCollector::begin_describe_node):
	Remove function.
	(TokenCollector::end_describe_node): Likewise.
	(TokenCollector::describe_node): Remove calls to begin/end.
	* ast/rust-ast-collector.h: Specialize begin and end collect items. Add
	more constructors to begin/end description.
	* ast/rust-ast-dump.cc (Dump::Dump): Adapt to new configuration
	options.
	* ast/rust-ast-dump.h: Add new configuration options.
	* rust-session-manager.cc (Session::dump_ast_pretty_internal): Use new
	configuration options.

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