Add Bash and Zsh completion scripts (#22646)

Add Bash and Zsh completion scripts (#22646)

This PR adds contrib scripts for bash and zsh completion.

Simply call:

```bash
source contrib/autocompletion/bash_autocomplete
```

or for Zsh:

```bash
source contrib/autocompletion/zsh_autocomplete
```

Signed-off-by: Andrew Thornton <art27@cantab.net>
---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: a1012112796 <1012112796@qq.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>