The field `uint64_t _ideal_phase_name_mask;` in DirectiveSet (used to store compiler directives) implicitly limits the number of phases in phasetype.hpp to 64. With the recent work on JDK-8295166, we are now surpassing this upper bound and need to remove it.

Compile::should_print_phase is the only function that makes use of _ideal_phase_name_mask.