* python3.8: bulk removal of now obsolete "_python38" packages.
Done via scripting. No functional change intended or expected.
Some manual tweaks will follow.
* python3.8: further manual tweaks after bulk-3.8-removal.
Unlike the previous commit with automated changes,
I've tested builds for *these* recipes in beta4 64 bits.
Switch to "installer" (instead of setuptools). Final package doesn't suffers
the problems mentioned on #7962 (no .py files, UKNOWN-0.0.0 as package
name-version).
