refactor(@angular-devkit/core): don't use concrete type as interface

Author: jkrems

goldens/public-api/angular_devkit/core/index.api.md

@@ -554,11 +554,11 @@ function oneLine(strings: TemplateStringsArray, ...values: any[]): string;
 function parseJsonPointer(pointer: JsonPointer): string[];
 
 // @public (undocumented)
-export class PartiallyOrderedSet<T> implements Set<T> {
+export class PartiallyOrderedSet<T> {
     // (undocumented)
     [Symbol.iterator](): IterableIterator<T, undefined, unknown>;
     // (undocumented)
-    get [Symbol.toStringTag](): 'Set';
+    get [Symbol.toStringTag](): 'PartiallyOrderedSet';
     // (undocumented)
     add(item: T, deps?: Set<T> | T[]): this;
     // (undocumented)

packages/angular_devkit/core/src/utils/partially-ordered-set.ts

@@ -19,7 +19,7 @@ export class CircularDependencyFoundException extends BaseException {
   }
 }
 
-export class PartiallyOrderedSet<T> implements Set<T> {
+export class PartiallyOrderedSet<T> {
   private _items = new Map<T, Set<T>>();
 
   protected _checkCircularDependencies(item: T, deps: Set<T>): void {
@@ -161,7 +161,7 @@ export class PartiallyOrderedSet<T> implements Set<T> {
     return undefined;
   }
 
-  get [Symbol.toStringTag](): 'Set' {
-    return 'Set';
+  get [Symbol.toStringTag](): 'PartiallyOrderedSet' {
+    return 'PartiallyOrderedSet';
   }
 }