Add NoGIL and Non-Debug builders on FreeBSD

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Add "AMD64 FreeBSD15 NoGIL" and "AMD64 FreeBSD16 Non-Debug".

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I spent hours debugging python/cpython#158893 issue, whereas it's very quick to reproduce on Free Threading. IMO Free Threading is important enough to need a builder on FreeBSD (15).

I also propose adding a Non-Debug builder on FreeBSD (16).

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First jobs:

• FreeBSD15 NoGIL: https://buildbot.python.org/#/builders/2364/builds/1
• FreeBSD16 Non-Debug: https://buildbot.python.org/#/builders/2370/builds/1

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FreeBSD15 NoGIL: https://buildbot.python.org/#/builders/2364/builds/1

And I found two bugs with this single run!

• Use _testlimitedcapi in test_free_threading.test_capi cpython#158935 : test_free_threading.test_capi fails with _ctypes extension is missing
• Fix @reap_threads usage in test_free_threading.test_json cpython#158937 : test_free_threading.test_json runs no test