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/upgrade/static/static.d.ts

@@ -0,0 +1,42 @@
+export declare function downgradeComponent(info: {
+    component: Type<any>;
+    downgradedModule?: string;
+    propagateDigest?: boolean;
+    /** @deprecated */ inputs?: string[];
+    /** @deprecated */ outputs?: string[];
+    /** @deprecated */ selectors?: string[];
+}): any;
+
+export declare function downgradeInjectable(token: any, downgradedModule?: string): Function;
+
+export declare function downgradeModule<T>(moduleFactoryOrBootstrapFn: NgModuleFactory<T> | ((extraProviders: StaticProvider[]) => Promise<NgModuleRef<T>>)): string;
+
+export declare function getAngularJSGlobal(): any;
+
+/** @deprecated */
+export declare function getAngularLib(): any;
+
+export declare function setAngularJSGlobal(ng: any): void;
+
+/** @deprecated */
+export declare function setAngularLib(ng: any): void;
+
+export declare class UpgradeComponent implements OnInit, OnChanges, DoCheck, OnDestroy {
+    constructor(name: string, elementRef: ElementRef, injector: Injector);
+    ngDoCheck(): void;
+    ngOnChanges(changes: SimpleChanges): void;
+    ngOnDestroy(): void;
+    ngOnInit(): void;
+}
+
+export declare class UpgradeModule {
+    $injector: any;
+    injector: Injector;
+    ngZone: NgZone;
+    constructor(
+    injector: Injector,
+    ngZone: NgZone);
+    bootstrap(element: Element, modules?: string[], config?: any): void;
+}
+
+export declare const VERSION: Version;

goldens/public-api/upgrade/static/testing/testing.d.ts

@@ -0,0 +1,3 @@
+export declare function createAngularJSTestingModule(angularModules: any[]): string;
+
+export declare function createAngularTestingModule(angularJSModules: string[], strictDi?: boolean): Type<any>;

goldens/public-api/upgrade/upgrade.d.ts

@@ -0,0 +1,24 @@
+/** @deprecated */
+export declare class UpgradeAdapter {
+    constructor(ng2AppModule: Type<any>, compilerOptions?: CompilerOptions | undefined);
+    bootstrap(element: Element, modules?: any[], config?: IAngularBootstrapConfig): UpgradeAdapterRef;
+    downgradeNg2Component(component: Type<any>): Function;
+    downgradeNg2Provider(token: any): Function;
+    registerForNg1Tests(modules?: string[]): UpgradeAdapterRef;
+    upgradeNg1Component(name: string): Type<any>;
+    upgradeNg1Provider(name: string, options?: {
+        asToken: any;
+    }): void;
+}
+
+/** @deprecated */
+export declare class UpgradeAdapterRef {
+    ng1Injector: IInjectorService;
+    ng1RootScope: IRootScopeService;
+    ng2Injector: Injector;
+    ng2ModuleRef: NgModuleRef<any>;
+    dispose(): void;
+    ready(fn: (upgradeAdapterRef: UpgradeAdapterRef) => void): void;
+}
+
+export declare const VERSION: Version;