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.
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