Remove hacking dir dependency from build backend (#81021)

* Copy man generation files into build backend

* Use copied files in build backend

MANIFEST.in

@@ -14,7 +14,7 @@ include licenses/*.txt
 include requirements.txt
 recursive-include docs *
 recursive-include hacking/build_library *.py
-recursive-include packaging *.py
+recursive-include packaging *.py *.j2
 recursive-include test/integration *
 recursive-include test/sanity *.in *.json *.py *.txt
 recursive-include test/support *.py *.ps1 *.psm1 *.cs *.md