fix(core/testing): clean up the core testing public API (#9466)

Previously, we were exporting internal mocks and helpers. Move these
to core/testing/testing_internal or remove them if they were
never used.

Remove deprecated items - injectAsync, clearPendingTimers.

BREAKING CHANGE:

Remove the following APIs from `@angular/core/testing`, which have been deprecated or were
never intended to be publicly exported:

```
injectAsync
clearPendingTimers
Log
MockAppliacationHref
MockNgZone
clearPendingTimers
getTypeOf
instantiateType
```

Instead of `injectAsync`, use `async(inject())`.

`clearPendingTimers` is no longer required.

modules/@angular/core/testing/testing.ts

@@ -12,9 +12,7 @@
  */
 import {isPromise, isString} from '../src/facade/lang';
 
-import {TestInjector, async, getTestInjector, inject, injectAsync} from './test_injector';
-
-export {async, inject, injectAsync} from './test_injector';
+import {TestInjector, getTestInjector} from './test_injector';
 
 declare var global: any;
 
@@ -79,6 +77,8 @@ var jsmIt = _global.it;
 var jsmIIt = _global.fit;
 var jsmXIt = _global.xit;
 
+// TODO(juliemr): override the globals and make them throw with a useful message.
+
 var testInjector: TestInjector = getTestInjector();
 
 // Reset the test providers before each test.