Migrate to Angular 12.1

Angular and related components (CDK, Flex Layout, Material) have been updated to version 12.x. Only a few minor code adjustment were necessary for compatibility.

After the update, the overall size of the build is reduced. While the initially loaded files are slightly smaller, the creator module now is noticeably smaller.

Related release notes and news:

• https://blog.angular.io/angular-v12-is-now-available-32ed51fbfd49
• https://github.com/angular/angular/releases/tag/11.2.0
• https://github.com/angular/angular/releases/tag/12.0.0
• https://github.com/angular/angular/releases/tag/12.1.0