This change reverts the removal of setBaseTestProviders that was
introduced in 8d746e3f6795c8840116f4649a37a1efb4243eb9.
Instead, setBaseTestProviders and the providers provided from
`@angular/platform-browser-dynamic/testing` and `@angular/server/testing`
will still work for the next release, but are deprecated.
See 8d746e3f6795c8840116f4649a37a1efb4243eb9 for how to upgrade.