Import test refcount

[wolfsage]

For Test-More/test-more#943

[wolfsage]

@leonerd This is almost a direct import of Test-Refcount. I've removed some tests that I don't think make sense to port over, and converted the rest of the tests and the module to use Test2::API etc...

Is this roughly what you imagined? I have not touched documentation, etc.

I'm not sure if you want identical modules with different code being maintained separately or not, or if one should point to the other, copyrights, so on and so forth...

[leonerd]

Is this roughly what you imagined? I have not touched documentation, etc.

I'm really not sure. It's an almost-exact copy of my original module so clearly it has the ability to test the same things I was looking for. But I can't speak for whether it's a good cultural fit for your ecosystem - in terms of names, argument types, operating style, etc... That was really the reason I didn't want to write it. I don't know what would fit with the rest of Test2

[wolfsage]

I did it this way so if both modules coexist, it should be easy to port fixes from one to the other since they look almost identical.

The other option is to maybe build Test::Refcount on top of Test2 and drop the Test::Builder, but then it won't be usable on any Test::More that predates the Test2 compatibility layer...

[exodist]

Maybe for this replace Test::More with Test2::V0 or similar

[wolfsage]

(Yes I did not touch the documentation basically at all because I wasn't sure how this was all going to look at the end :))

[exodist]

The main docs refer to Test::More, it should probably be Test2::V0 instead for this PR.
The provided tools are fine
I would also maybe add an optional export for refcount(). I think in Test2 the most likely usage would be:

is(refcount($foo), 5);   but I am fine with is_refcount() or refcount_is() also existing.

is_oneref() is very good to have too.

[wolfsage]

Thanks for the review, will try to find time for that soon

[wolfsage]

Hey thanks!