Switch to RepoUrlPicker to fill repository information

[schultzp2020]

The RepoUrlPicker will automatically ask the corresponding information for each type of repository.

e.g. https://github.com/backstage/software-templates/blob/main/scaffolder-templates/react-ssr-template/template.yaml#L43

[Zaperex]

The main issue I've found with the RepoUrlPicker at the moment is that the allowedHosts only supports a list of hardcoded host urls in the template. So if the user wants to use a private host instance, they'll need to directly modify the template to include them, and refresh/re-ingest them.

Leaving the allowedHosts field blank, or not providing it causes the allow list to default to [] meaning nothing is allowed.

[schultzp2020]

So if the user wants to use a private host instance, they'll need to directly modify the template to include them, and refresh/re-ingest them.

@Zaperex that is ok because we expect the users to modify the templates. For now lets hold off on this issue because RepoUrlPicker is still missing some key features.