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/testing/testing.d.ts

@@ -0,0 +1,142 @@
+export declare function async(fn: Function): (done: any) => any;
+
+export declare class ComponentFixture<T> {
+    changeDetectorRef: ChangeDetectorRef;
+    componentInstance: T;
+    componentRef: ComponentRef<T>;
+    debugElement: DebugElement;
+    elementRef: ElementRef;
+    nativeElement: any;
+    ngZone: NgZone | null;
+    constructor(componentRef: ComponentRef<T>, ngZone: NgZone | null, _autoDetect: boolean);
+    autoDetectChanges(autoDetect?: boolean): void;
+    checkNoChanges(): void;
+    destroy(): void;
+    detectChanges(checkNoChanges?: boolean): void;
+    isStable(): boolean;
+    whenRenderingDone(): Promise<any>;
+    whenStable(): Promise<any>;
+}
+
+export declare const ComponentFixtureAutoDetect: InjectionToken<boolean[]>;
+
+export declare const ComponentFixtureNoNgZone: InjectionToken<boolean[]>;
+
+export declare function discardPeriodicTasks(): void;
+
+export declare function fakeAsync(fn: Function): (...args: any[]) => any;
+
+export declare function flush(maxTurns?: number): number;
+
+export declare function flushMicrotasks(): void;
+
+export declare const getTestBed: () => TestBed;
+
+export declare function inject(tokens: any[], fn: Function): () => any;
+
+export declare class InjectSetupWrapper {
+    constructor(_moduleDef: () => TestModuleMetadata);
+    inject(tokens: any[], fn: Function): () => any;
+}
+
+export declare type MetadataOverride<T> = {
+    add?: Partial<T>;
+    remove?: Partial<T>;
+    set?: Partial<T>;
+};
+
+export declare function resetFakeAsyncZone(): void;
+
+export declare interface TestBed {
+    ngModule: Type<any> | Type<any>[];
+    platform: PlatformRef;
+    compileComponents(): Promise<any>;
+    configureCompiler(config: {
+        providers?: any[];
+        useJit?: boolean;
+    }): void;
+    configureTestingModule(moduleDef: TestModuleMetadata): void;
+    createComponent<T>(component: Type<T>): ComponentFixture<T>;
+    execute(tokens: any[], fn: Function, context?: any): any;
+    /** @deprecated */ get<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: T, flags?: InjectFlags): any;
+    /** @deprecated */ get(token: any, notFoundValue?: any): any;
+    initTestEnvironment(ngModule: Type<any> | Type<any>[], platform: PlatformRef, aotSummaries?: () => any[]): void;
+    inject<T>(token: Type<T> | InjectionToken<T> | AbstractType<T>, notFoundValue?: T, flags?: InjectFlags): T;
+    inject<T>(token: Type<T> | InjectionToken<T> | AbstractType<T>, notFoundValue: null, flags?: InjectFlags): T | null;
+    overrideComponent(component: Type<any>, override: MetadataOverride<Component>): void;
+    overrideDirective(directive: Type<any>, override: MetadataOverride<Directive>): void;
+    overrideModule(ngModule: Type<any>, override: MetadataOverride<NgModule>): void;
+    overridePipe(pipe: Type<any>, override: MetadataOverride<Pipe>): void;
+    overrideProvider(token: any, provider: {
+        useFactory: Function;
+        deps: any[];
+    }): void;
+    overrideProvider(token: any, provider: {
+        useValue: any;
+    }): void;
+    overrideProvider(token: any, provider: {
+        useFactory?: Function;
+        useValue?: any;
+        deps?: any[];
+    }): void;
+    overrideTemplateUsingTestingModule(component: Type<any>, template: string): void;
+    resetTestEnvironment(): void;
+    resetTestingModule(): void;
+}
+
+export declare const TestBed: TestBedStatic;
+
+export declare interface TestBedStatic {
+    new (...args: any[]): TestBed;
+    compileComponents(): Promise<any>;
+    configureCompiler(config: {
+        providers?: any[];
+        useJit?: boolean;
+    }): TestBedStatic;
+    configureTestingModule(moduleDef: TestModuleMetadata): TestBedStatic;
+    createComponent<T>(component: Type<T>): ComponentFixture<T>;
+    /** @deprecated */ get<T>(token: Type<T> | InjectionToken<T>, notFoundValue?: T, flags?: InjectFlags): any;
+    /** @deprecated */ get(token: any, notFoundValue?: any): any;
+    initTestEnvironment(ngModule: Type<any> | Type<any>[], platform: PlatformRef, aotSummaries?: () => any[]): TestBed;
+    inject<T>(token: Type<T> | InjectionToken<T> | AbstractType<T>, notFoundValue?: T, flags?: InjectFlags): T;
+    inject<T>(token: Type<T> | InjectionToken<T> | AbstractType<T>, notFoundValue: null, flags?: InjectFlags): T | null;
+    overrideComponent(component: Type<any>, override: MetadataOverride<Component>): TestBedStatic;
+    overrideDirective(directive: Type<any>, override: MetadataOverride<Directive>): TestBedStatic;
+    overrideModule(ngModule: Type<any>, override: MetadataOverride<NgModule>): TestBedStatic;
+    overridePipe(pipe: Type<any>, override: MetadataOverride<Pipe>): TestBedStatic;
+    overrideProvider(token: any, provider: {
+        useFactory: Function;
+        deps: any[];
+    }): TestBedStatic;
+    overrideProvider(token: any, provider: {
+        useValue: any;
+    }): TestBedStatic;
+    overrideProvider(token: any, provider: {
+        useFactory?: Function;
+        useValue?: any;
+        deps?: any[];
+    }): TestBedStatic;
+    overrideTemplate(component: Type<any>, template: string): TestBedStatic;
+    overrideTemplateUsingTestingModule(component: Type<any>, template: string): TestBedStatic;
+    resetTestEnvironment(): void;
+    resetTestingModule(): TestBedStatic;
+}
+
+export declare class TestComponentRenderer {
+    insertRootElement(rootElementId: string): void;
+}
+
+export declare type TestModuleMetadata = {
+    providers?: any[];
+    declarations?: any[];
+    imports?: any[];
+    schemas?: Array<SchemaMetadata | any[]>;
+    aotSummaries?: () => any[];
+};
+
+export declare function tick(millis?: number, tickOptions?: {
+    processNewMacroTasksSynchronously: boolean;
+}): void;
+
+export declare function withModule(moduleDef: TestModuleMetadata): InjectSetupWrapper;
+export declare function withModule(moduleDef: TestModuleMetadata, fn: Function): () => any;