New capability can_generate_early_class_hook_events

Some agents need to get a CFLH event for classes loaded in the primordial phase. This is not possible in JDK 9 because existing agents may instrument code in the primordial or start phase before the module system has completed initialization.

One way that we could allow this is if we introduce a new capability, say can_generate_early_class_hook_events. If this capability and can_generate_all_class_hook_events are enabled then the CFLH event could be posted in the primordial phase.