Add `extern "C"` around `PyTraceMalloc_` functions. (#127772)
Pretty much everything else exported by Python.h has an extern "C"
annotation, yet this header appears to be missing one.
(cherry picked from commit 2cdeb61b57)
Co-authored-by: Peter Hawkins <hawkinsp@cs.stanford.edu>
_PyTraceMalloc_NewReference() is now called by _Py_NewReference(), so
move its definition to object.h. Moreover, define it even if
Py_LIMITED_API is defined, since _Py_NewReference() is also exposed
even if Py_LIMITED_API is defined.
* Modify object.h to ensure that pymem.h is included,
to get _Py_tracemalloc_config variable.
* Move _PyTraceMalloc_XXX() functions to tracemalloc.h,
they need PyObject type. Break circular dependency between pymem.h
and object.h.
