validate meta/main.yml dependencies and meta/requirements.yml are lists

[s-hertel]

SUMMARY

Fix an unhandled traceback and give a clear error when installing roles dependencies that are in collection + role requirement file format, e.g.

collections:
  - ns.coll
roles:
  - role

This matches role runtime behavior for meta/main.yml dependencies which must be a list of roles.

Alternative approach to #73480, which adds support for that format with a warning if collections key is provided.
Closes #73480

ISSUE TYPE

• Bugfix Pull Request