The testing_e2e util does not belong in platform-browser and was never
intended to be a public API. Move it out of that whole tree.
BREAKING CHANGE:
The following API was never intended to be public and is removed:
```js
import {verifyNoBrowserErrors} from '@angular/platform-browser/testing_e2e';
```
Consider using Protractor's console plugin: https://github.com/angular/protractor-console-plugin
- 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#9236Closes#9235
Ref #9234
