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/examples/platform-browser/dom/debug/ts/debug_element_view_listener/providers.ts

@@ -7,7 +7,6 @@
  */
 
 import {Component} from '@angular/core';
-import {ELEMENT_PROBE_PROVIDERS} from '@angular/platform-browser';
 import {bootstrap} from '@angular/platform-browser-dynamic';
 
 @Component({selector: 'my-component'})
@@ -15,5 +14,5 @@ class MyAppComponent {
 }
 
 // #docregion providers
-bootstrap(MyAppComponent, [ELEMENT_PROBE_PROVIDERS]);
+bootstrap(MyAppComponent);
 // #enddocregion