chore(imports): don't import ExceptionHandler from facade (#10620)

This lets us skip src/facade/exception* when compiling modules other than core.
It prevents having many conflicting declarations

modules/@angular/compiler/testing/metadata_overrider.ts

@@ -6,9 +6,9 @@
  * found in the LICENSE file at https://angular.io/license
  */
 
+import {BaseException} from '@angular/core';
 import {MetadataOverride} from '@angular/core/testing';
 
-import {BaseException} from '../src/facade/exceptions';
 import {ConcreteType, stringify} from '../src/facade/lang';
 
 type StringMap = {