nixos/autosuggestions: add module (#41397)

The `zsh-autosuggestions` package provides several configuration options
such as a different highlight style (like `fg=cyan` which is easier to
read).

With `rename.nix` the old `programs.zsh.enableAutosuggestions` is still
functional, but yields the following warning like this during evaluation:

```
trace: warning: The option `programs.zsh.enableAutosuggestions' defined in `<unknown-file>' has been renamed to `programs.zsh.autosuggestions.enable'.
```

The module provides the most common `zsh-autosuggestions` (highlight
style and strategy) as options that will be written into the interactive
shell init (`/etc/zshrc` by default). Further configuration options can
be declared using the `extraConfig` attr set:

```
{
  programs.zsh.autosuggestions.extraConfig = {
    "ZSH_AUTOSUGGEST_BUFFER_MAX_SIZE" = "buffer_size";
  };
}
```

A full list of available configuration options for `zsh-autosuggestions`
can be viewed here: https://github.com/zsh-users/zsh-autosuggestions/blob/v0.4.3/README.md