Investigate if hooks should be ported to Go

Gitaly is migrating the Git Hooks from GitLab-Shell, #1226 (closed). Once that migration is completed, it might be an idea to migrate these to Go. Advantages might be:

1. Faster start up time
2. Ability to use external pacakges in the hooks. With Ruby we can't use gems
3. Code reuse with Gitaly
4. Control over the runtime, with Ruby we might not know what Ruby we're running

There are downsides too; for one that such a migration is not without its own risks.