feat(@angular-devkit/build-angular): drop support for ng-packagr version 11

BREAKING CHANGE:

Minimum supported `ng-packagr` version is `12.0.0-next`

Author: alan-agius4

packages/angular_devkit/build_angular/package.json

@@ -83,7 +83,7 @@
     "@angular/localize": "^11.0.0 || ^11.2.0-next",
     "@angular/service-worker": "^11.0.0 || ^11.2.0-next",
     "karma": "^6.0.0",
-    "ng-packagr": "^11.0.0 || ^11.2.0-next",
+    "ng-packagr": "^12.0.0-next",
     "protractor": "^7.0.0",
     "tailwindcss": "^2.0.0",
     "tslint": "^6.1.0",