…TestBed error handler

The internal error handler in TestBed rethrows errors to prevent them
from being silently ignored in tests. Prior to this commit, tests which
used `provideZoneChangeDetection` in the providers would override the
internal error handler of TestBed and prevent these errors from being
rethrown.

BREAKING CHANGE: (test only) - Using `provideZoneChangeDetection` in the
TestBed providers would previously prevent `TestBed` from rethrowing
errors as it should. Errors in the test will now be rethrown, regardless
of the usage of `provideZoneChangeDetection`. Tests should be adjusted to
prevent or account for these errors. As in previous major versions,
this behavior can be disabled with `rethrowApplicationErrors: false` in
`configureTestingModule` as a last resort.