Fix Py Extensions & Install .pyi Files

- The python runtime extension files did shadow the actual pybind
  classes we declare for `ImpactXParIter` and a few others, because
  the module name was the same.
- `.pyi` stub files were not yet installed.

setup.py

@@ -29,31 +29,17 @@ def initialize_options(self):
     def run(self):
         # remove existing build directory
         #   by default, this stays around. we want to make sure generated
-        #   files like libwarpx.(2d|3d|rz).(so|pyd) are always only the
+        #   files like libimpactx.(so|pyd) are always only the
         #   ones we want to package and not ones from an earlier wheel's stage
         if os.path.exists(self.build_base):
             shutil.rmtree(self.build_base)
 
         # call superclass
         build.run(self)
 
-        # matches: impactx_pybind.*.(so|pyd)
-        re_libprefix = re.compile(r"impactx_pybind\..*\.(?:so|pyd)")
-        libs_found = []
-        for lib_name in os.listdir(PYIMPACTX_libdir):
-            if re_libprefix.match(lib_name):
-                lib_path = os.path.join(PYIMPACTX_libdir, lib_name)
-                libs_found.append(lib_path)
-        if len(libs_found) == 0:
-            raise RuntimeError(
-                "Error: no pre-build pyImpactX libraries found in "
-                "PYIMPACTX_libdir='{}'".format(PYIMPACTX_libdir)
-            )
-
-        # copy external libs into collection of files in a temporary build dir
+        # copy Python module artifacts and sources
         dst_path = os.path.join(self.build_lib, "impactx")
-        for lib_path in libs_found:
-            shutil.copy(lib_path, dst_path)
+        shutil.copytree(PYIMPACTX_libdir, dst_path, dirs_exist_ok=True)
 
 
 class CMakeExtension(Extension):

src/python/impactx/__init__.py

@@ -18,9 +18,11 @@
 
 # import core bindings to C++
 from . import impactx_pybind as cxx
+from .extensions.ImpactXParIter import register_ImpactXParIter_extension
+from .extensions.ImpactXParticleContainer import (
+    register_ImpactXParticleContainer_extension,
+)
 from .impactx_pybind import *  # noqa
-from .ImpactXParIter import register_ImpactXParIter_extension
-from .ImpactXParticleContainer import register_ImpactXParticleContainer_extension
 from .madx_to_impactx import read_beam, read_lattice  # noqa
 
 __version__ = cxx.__version__