…ampling

… gvl

…e state

This test helper method was getting very annoying to maintain every
time we needed to test new features.

The flakiness on this spec showed up again when I slightly refactored
the `Collectors::Stack::Testing._native_sample` method but goes away if
we use an array.

I really dislike all the handwaving around this, but I'm not sure what
we can do better in this case.

We're using low-level Ruby APIs that don't look before they jump, so
let's be careful to do our own validation to avoid crashes.

It occurs to me that I'm sprinkling a lot of conditionals all over the
place, and when we want to support 3.2 we'll need to find all of them
and if we miss some there won't be anything reminding us it's missing.

So by extracting the version to a single location, we'll bump it once
and all specs that need to work for 3.2 will be run.

So far in the profiler, we've been avoiding adding defaults to keyword
arguments that are expected to be set in production as, well, those
defaults won't match what happens in production (they'll get
overridden).

This is all fine, but quite annoying when we use our components
piecemeal for benchmarking and testing, since adding any new arguments
means modifying a gazillion places in the codebase to start passing in
that argument.

To solve this, let's introduce a `for_testing` helper method that
provides defaults that we often use for testing, and that then calls
into the regular constructor.

…dcoded

This setting is going to be the main overhead lever for the Waiting for
GVL feature. Having it configurable will allow us to play with it and
better find good defaults.

This method has way too many positional arguments, let's try to avoid
this footgun by using keyword arguments instead.

…imeWorker

+ a small refactor for skipping GVL profiling specs on legacy Rubies

This skip was only called after a previous before started the profiler,
so this left the test suite in an incorrect state.

…d argument warning

…ubies