bpo-41089: Filters and other issues in Visual Studio projects (GH-21070)

* Add missing header files to pythoncore.
* Add missing file filters ("Resource Files" in particular) to
  all projects.
* Add new sub-filters for private headers in pythoncore and
  for 3rd party source files.
* Add missing _zoneinfo configurations in pcbuild.sln.
* Update bdist_wininst with the new zlib location.