gh-106320: Remove private _PyDict function

[vstinner]

Move private _PyDict functions to the internal C API (pycore_dict.h):

• _PyDictView_Intersect()
• _PyDictView_New()
• _PyDict_ContainsId()
• _PyDict_DelItemId()
• _PyDict_DelItem_KnownHash()
• _PyDict_GetItemIdWithError()
• _PyDict_GetItem_KnownHash()
• _PyDict_HasSplitTable()
• _PyDict_NewPresized()
• _PyDict_Next()
• _PyDict_Pop()
• _PyDict_SetItemId()
• _PyDict_SetItem_KnownHash()
• _PyDict_SizeOf()

No longer export most of these functions.

Move also the _PyDictViewObject to the internal C API.

Move dict_getitem_knownhash() function from _testcapi to the _testinternalcapi extension. Update test_capi.test_dict for this move.

• Issue: C API: Remove private C API functions (move them to the internal C API) #106320

[eendebakpt]

@vstinner In this PR the method _PyDict_NewPresized was moved to the internal API. According to https://devguide.python.org/developer-workflow/c-api/#with-the-extern-keyword the method should still be available for stdlib extensions.

I am using the method in an extension module #91610, but the build is failing since this PR was merged with error message Error: _copy failed to import: /home/runner/work/cpython/cpython-builddir/build/lib.linux-x86_64-3.13-pydebug/_copy.cpython-313d-x86_64-linux-gnu.so: undefined symbol: _PyDict_NewPresized (but the build is successful for Windows platforms).

I added the correct header file #include "pycore_dict.h" and macros Py_BUILD_CORE_MODULE and Py_BUILD_CORE_BUILTIN. What else needs to be done to make use of _PyDict_NewPresized?

[vstinner]

I am using the method in an extension module #91610, but the build is failing since this PR was merged with error message Error: _copy failed to import: /home/runner/work/cpython/cpython-builddir/build/lib.linux-x86_64-3.13-pydebug/_copy.cpython-313d-x86_64-linux-gnu.so: undefined symbol: _PyDict_NewPresized (but the build is successful for Windows platforms).

If you want to use this function in a stdlib extension, you should replace extern with PyAPI_FUNC(). It's required to be able to use the function in extensions built as shared libraries.