fix: public api surface fixes + stability markers

- ts-api-guardian will now error if a new public symbol is added with a stability marker (`@stable`, `@experimental`, `@deprecated`)
- DomEventsPlugin and KeyEventsPlugin were removed from public api surface - these classes is an implementation detail
- deprecated BROWSER_PROVIDERS was removed completely
- `@angular/compiler` was removed from the ts-api-guardian check since this package shouldn't contain anything that users need to directly import
- the rest of the api surface was conservatively marked as stable or experimental

BREAKING CHANGES: DomEventsPlugin and KeyEventsPlugin previously exported from core are no longer public - these classes are implementation detail.

Previously deprecated BROWSER_PROVIDERS was completely removed from platform-browser.

Closes #9236
Closes #9235
Ref #9234

modules/@angular/core/src/linker/component_factory.ts

@@ -86,6 +86,10 @@ export class ComponentRef_<C> extends ComponentRef<C> {
  * @ts2dart_const
  */
 const EMPTY_CONTEXT = /*@ts2dart_const*/ new Object();
+
+/**
+ * @stable
+ */
 export class ComponentFactory<C> {
   constructor(
       public selector: string, private _viewFactory: Function, private _componentType: Type) {}

modules/@angular/core/src/linker/component_factory_resolver.ts

@@ -12,6 +12,10 @@ import {ClassWithConstructor, stringify} from '../facade/lang';
 
 import {ComponentFactory} from './component_factory';
 
+
+/**
+ * @stable
+ */
 export class NoComponentFactoryError extends BaseException {
   constructor(public component: Function) {
     super(`No component factory found for ${stringify(component)}`);
@@ -24,6 +28,9 @@ class _NullComponentFactoryResolver implements ComponentFactoryResolver {
   }
 }
 
+/**
+ * @stable
+ */
 export abstract class ComponentFactoryResolver {
   static NULL: ComponentFactoryResolver = new _NullComponentFactoryResolver();
   abstract resolveComponentFactory<T>(component: ClassWithConstructor<T>): ComponentFactory<T>;

modules/@angular/core/src/linker/element_ref.ts

@@ -11,6 +11,8 @@
  *
  * An `ElementRef` is backed by a render-specific element. In the browser, this is usually a DOM
  * element.
+ *
+ * @stable
  */
 // Note: We don't expose things like `Injector`, `ViewContainer`, ... here,
 // i.e. users have to ask for what they need. With that, we can build better analysis tools