analyzer: reduce use of naked "new" for json dumps

analyzer: reduce use of naked "new" for json dumps

No functional change intended.

gcc/analyzer/ChangeLog:
	* call-string.cc (call_string::to_json): Avoid naked "new".
	* constraint-manager.cc (bounded_range::set_json_attr): Likewise.
	(equiv_class::to_json): Likewise.
	(constraint::to_json): Likewise.
	(bounded_ranges_constraint::to_json): Likewise.
	* diagnostic-manager.cc (saved_diagnostic::to_json): Likewise.
	(saved_diagnostic::maybe_add_sarif_properties): Likewise.
	* engine.cc (exploded_node::to_json): Likewise.
	(exploded_edge::to_json): Likewise.
	* program-point.cc (program_point::to_json): Likewise.
	* program-state.cc (program_state::to_json): Likewise.
	* sm.cc (state_machine::to_json): Likewise.
	* store.cc (binding_cluster::to_json): Likewise.
	(store::to_json): Likewise.
	* supergraph.cc (supernode::to_json): Likewise.
	(superedge::to_json): Likewise.

Signed-off-by: David Malcolm <dmalcolm@redhat.com>