Code refactor proposal: Major change in rehash hook

[ChristianFredrikJohnsen]

I was looking at optimizing rehash, and noticed that a bunch of time was spent sourcing the scripts:

conda.bash and source.bash, both in pyenv.d/exec.

I have done some slight optimizations in conda.bash, but I don't know about the source.bash file.
It was created in this pull request which says source.bash is a temporary fix for something. But as you can see further down the line, the problem seems to not even be solved with this merge (talking about the gettext.sh). I have not been able to reproduce that problem.

In any case, I am questioning whether these source scripts are even being used. They don't work at all for me, partly because I am using zsh, and there is no shebang in the prototype shim:

cat > "${PROTOTYPE_SOURCE_SHIM_PATH}" <<SH
[ -n "\$PYENV_DEBUG" ] && set -x
export PYENV_ROOT="${PYENV_ROOT}"
program="\$("$(command -v pyenv)" which "\${BASH_SOURCE##*/}")"
if [ -e "\${program}" ]; then
  . "\${program}" "\$@"
fi
SH

So it's trying to use BASH_SOURCE, but of course, it returns "" (empty string), because I am not using bash.
Second, the activate function (as an example)

# virtualenv
activate
activate.csh
activate.fish
activate.nu
# gettext (#688)
gettext.sh

Doesn't even work. Well, first you need to make sure that you do init of virtualenv before init of pyenv in ~/.zshrc, since if not, you will use the activate function of virtualenv, which I guess this setup is trying to override.
But even if I try this activate which is generated by pyenv.d/rehashsource.bash`, I just get this output:

activate saus
pyenv-virtualenv: activate saus

And the python version does not change. The entire setup is extremely messy.
I don't see the use of this activate command at all, and I am wondering if it can be removed entirely.