bpo-29778: Ensure python3.dll is loaded from correct locations when Python is embedded (GH-21297)


Also enables using debug build of `python3_d.dll`
Reference: CVE-2020-15523
(cherry picked from commit dcbaa1b49cd9062fb9ba2b9d49555ac6cd8c60b5)

Co-authored-by: Steve Dower <steve.dower@python.org>
diff --git a/PCbuild/python.props b/PCbuild/python.props
index 6388d1b..bf6f371 100644
--- a/PCbuild/python.props
+++ b/PCbuild/python.props
@@ -203,6 +203,8 @@
     
     <!-- The name of the resulting pythonXY.dll (without the extension) -->
     <PyDllName>python$(MajorVersionNumber)$(MinorVersionNumber)$(PyDebugExt)</PyDllName>
+    <!-- The name of the resulting pythonX.dll (without the extension) -->
+    <Py3DllName>python3$(PyDebugExt)</Py3DllName>
 
     <!-- The version and platform tag to include in .pyd filenames -->
     <PydTag Condition="$(ArchName) == 'win32'">.cp$(MajorVersionNumber)$(MinorVersionNumber)-win32</PydTag>