ci: move public-api goldens to goldens directory (#35768)

Moves the public api .d.ts files from tools/public_api_guard to
goldens/public-api.

Additionally, provides a README in the goldens directory and a script
assist in testing the current state of the repo against the goldens as
well as a command for accepting all changes to the goldens in a single
command.

PR Close #35768

goldens/public-api/core/global_utils.d.ts

@@ -0,0 +1,25 @@
+export declare function applyChanges(component: {}): void;
+
+export declare function getComponent<T>(element: Element): T | null;
+
+export declare function getContext<T>(element: Element): T | null;
+
+export declare function getDirectives(element: Element): {}[];
+
+export declare function getHostElement(componentOrDirective: {}): Element;
+
+export declare function getInjector(elementOrDir: Element | {}): Injector;
+
+export declare function getListeners(element: Element): Listener[];
+
+export declare function getOwningComponent<T>(elementOrDir: Element | {}): T | null;
+
+export declare function getRootComponents(elementOrDir: Element | {}): {}[];
+
+export interface Listener {
+    callback: (value: any) => any;
+    element: Element;
+    name: string;
+    type: 'dom' | 'output';
+    useCapture: boolean;
+}