auto detect current deploytype when running commands

instead of requiring user input to select deployType every time, deployType correlates 1:1 with the presence of templated folders

```
./charts -> helm
./base && ./overlays -> kustomize
./manifests -> manifests
```

at minimum, when calling generate-workflow, draft could detect if only one of these is present, and default to it instead of prompting for selection every time

additionally, abstracting the ability to update images in a deployType-agnositc interface would greatly simplify the code
https://github.com/Azure/draft/blob/040260598e8ef05018c992dc09244cd572901628/pkg/workflows/workflows.go#L37