[Feature Request] Allow optional control over vertical and horizontal display

## Request
The current implementation defaults to horizontal, so only horizontal views are generated.
https://github.com/awslabs/diagram-as-code/blob/601056c873298e2f2312b3f3ffbe8be6b458d77c/internal/types/group.go#L55


It's better to be able to switch the display with an option.

### Example
```
$ awsdac --cfn-template --vertical
```


Start with internal/types/group.go at the linked default layout setting, then trace how the awsdac command parses options and generates diagrams. Add the requested vertical or horizontal control while preserving the current horizontal default. Done means the example command produces a vertical diagram and existing horizontal output remains unchanged.

Written by the indexing model from the issue text.