* Split long.c tests of _testcapi into two parts: limited C API tests
in _testlimitedcapi and non-limited C API tests in _testcapi.
* Move testcapi_long.h from Modules/_testcapi/ to
Modules/_testlimitedcapi/.
* Add MODULE__TESTLIMITEDCAPI_DEPS to Makefile.pre.in.
This expands the examples to cover both realistic use cases for the API.
I noticed thing in the test that could be done better so I added those as well: We need to guarantee that all bytes of the result are overwritten and that too many are not written. Tests now pre-fills the result with data in order to ensure that.
Co-authored-by: Steve Dower <steve.dower@microsoft.com>