While gitlab-shell currently has a major version of v14, the module path
it exposes is not using that major version like it is required by the Go
standard. This makes it impossible for dependents to import gitlab-shell
as a dependency without using a commit as version.

Fix this by changing the module path of gitlab-shell to instead be
`gitlab.com/gitlab-org/gitlab-shell/v14` and adjust all imports
accordingly.

Changelog: fixed

parse logic will only run if the executable accept args.
healthcheck is the only one not accepting arguments.

We had `gitlab-shell-authorized-keys-check` and
`gitlab-shell-authorized-principals-check` as symlinks to
`gitlab-shell` before.

We determine the `Command` and `CommandArgs` that we build based
on the `Name` of the `Executable`. We also use that to know which
fallback ruby executable should we fallback to. We use
`os.Executable()` to do that.

`os.Executable()` behaves differently depending on OS. It may
return the symlink or the target's name. That can result to a
buggy behavior.

The fix is to create binaries for each instead of using a symlink.
That way we don't need to rely on `os.Executable()` to get the name.
We pass the `Name` of the executable instead.

This struct is responsible for determining the name and
root dir of the executable.

The `RootDir` property will be used to find the config.

The `Name` property will be used to determine what `Command`
and `CommandArgs` to be built.