RubyKernel defines a different MethodMissingMethod that is the
base of all special builtin method_missing methods.

The producers here are not prevented from running, which may lead
to them completing before the status checks below. This in turn
causes deprecation warnings when =~ is called on the false object.

This also patches the status checks to avoid ever calling =~ on a
non-stringlike object.

See ruby/ruby#7830 for a more detailed
explanation.

This spec was added to ensure that suspended fibers silently die
when their parent thread is terminated, but we disagree as to
whether thread-terminating events should trigger ensures in child
threads. In JRuby, where fibers are backed by either an OS thread
or a virtual thread, ensures currently will always run on the way
out of a fiber, ensuring held resources are properly cleaned up.
We tag this spec because we disagree with the assessment that
ensures should not run for suspended fibers.