* Don't bother reading empty version files
* Implement version file read in pure bash
Is faster with usual sized version files, slower with degenerate cases.

Don't use Homebrew outside of MacOS

In Linux, it's not the primary source of packages and
cannot be used without build flag adjustments
thus has caused build failures.

Simplify init scheme

We're going to eliminate the need to mandatorily use `pyenv init --path`.
We can't delete it yet for backward compatibility.
Besides, there's one other use case for it: to enable shims but without
shell integration, e.g. for noninteractive shells.

To be a full-fledged replacement for `pyenv init -` however,
it needs to do rehashing.

Now the setup is to add to both rc and profile:
1) set PYENV_ROOT
   (can do it unconditionally -- since if you change it,
   you need to update all places anyway since any of them can be run first)
2) Add `pyenv` to PATH if not already there
3) eval "$(pyenv init -)"

Not a breaking change, old setup will continue to work.

Required for diagnostics

Trace logs without `-v` are usually useless due to missing the build part.
So this leaves one less thing for users to worry about
when submitting error reports.

Mentioning `-v` in the issue template should stay for some time
since users report on old versions, too.

There are no new (glaring) platform incompatibilities in MacOS 12 so those releases should technically run in it as well

Co-authored-by: Dan Dees <dand@appsmiths.com>

I've never been able to activate (or refund) existing bounties on solved problems. Their support has been unhelpful. So I've given up on them.

Fixes https://github.com/pyenv/pyenv/issues/2278

All the patches still apply

Co-authored-by: Dan Dees <dand@appsmiths.com>