Move patterns from theme to module

Problem/Motivation

Pagedesigner relies on the ui_patterns module, which allows users to place structural elements (rows) on a page to build a layout, and to populate those rows with design elements. In principle, ui_patterns patterns can be defined in yml files in a theme or module. Currently no patterns are designed in the module. Therefore, users who want to evaluate Pagedesigner, or use it in a basic setup, must define patterns in code before anything happens.

The pagedesigner_theme does provide some example patterns. However, it is not maintained, and cannot be installed on Drupal 9 using composer. I leave aside the option of using the 'lenient' option which allows to composer to install Drupal 8 module on Drupal 9, because it tends to lead to a composer setup which is broken in other ways and frustratingly hard to fix.

Proposed resolution

1. Move the example patterns currently in pagedesigner_theme into the module, so that Pagedesigner can be evaluated with any theme.
2. Create additional patterns, so that users have the option of a more fully-featured Pagedesigner installation without writing their own patterns.