this PR allows you to install python via `asdf install python 3.10` or
`asdf install python 3`. It will then install the latest version
starting with that prefix.
It will add an alias in ~/.asdf/installs/python so you can have a
.tool-versions file like the following:
```
python 3.10
```
I hope this isn't too controversial: I personally have this
`ASDF_PYTHON_PATCHES_DIRECTORY` globally set up on my machine, which is
super useful when I install/reinstall random versions of Python, but is
kind of annoying when I try to install versions of python that don't
actually need a patch: I have to create an empty file just to get it to
install.
With this change, I don't have to do that: instead I only have to create
`.patch` files for the versions of Python that need it.
`python-build` supports a `-p` option to patch Python before installing. In
particular, I use this to apply a patch for OS X Big Sur before installing
older versions of Python.
I'm not super-wedded to this particular implementation: opening this PR for
more discussion.
