feat(@schematics/angular): add guardType as an alias of implements in guard schematic

`implements` option will be removed in future in favor of `guardType`. This is because the implements guard pattern is deprecated in version 15.1

Author: alan-agius4

packages/schematics/angular/guard/schema.json

@@ -47,6 +47,7 @@
  "default": false
  },
  "implements": {
+ "alias": "guardType",
  "type": "array",
  "description": "Specifies which type of guard to create.",
  "uniqueItems": true,