Pyenv shims break all attempted executions for pythons not in versions list

[techalchemy]

When versions are missing from the version file in $PYENV_ROOT, pyenv will still create shims for them but will fail to redirect commands, thereby breaking all execution locally for users.

For our purposes, lets just remove shims from finder paths, respect the order specified in the global version setting, and order by cpython interpreter versions first in descending order (non-prereleases first), then alphabetically, since we can use every pyenv path. in order.

ref pypa/pipenv#3124

see also pyenv/pyenv#1185, pyenv/pyenv#1112