…turn value

…ethods

An instance of `CleanupActions` must exist for each _invocation_,
not for each _invoker_. This requires some creative juggling of
method handle arguments, which is what this commit does.

…entations

…ing the ultimate invocation

This currently doesn't help anything, but it should be possible
to optimize out `CleanupActions` instantiation completely when
we know that it is never used.

This required moving the invoker construction logic from `InvokerImpl`
into the `AbstractInvokerBuilder`, which is arguably a better place anyway.
The `InvokerImpl` looks fairly minimal now, as it should.

…l the time

…now be created from any method

…n WFLY. Use this in CI jobs.