Problem/Motivation
There's no need to maintain the drupal/legacy-project starting point. This composer template existed to help people migrate to using composer from drupal/drupal projects. Let's remove it and only have one template to start from.
Existing projects are unaffected as the template is only used during creation and if new projects want the same layout they can always change their scaffold settings to something similar but we shouldn't be making it easy to start a project with vendor in the web root.
Proposed resolution
Remove it.
Remaining tasks
User interface changes
NOne
API changes
None
Data model changes
None
Release notes snippet
The drupal/legacy-project composer template is removed. Existing sites that used the template to start from are unaffected. The drupal/recommended-project composer template is the only starting point provided by Drupal core.