`zone.js` 0.8.25 introduces `zone-testing` bundle and move all `fakeAsync/async` logic
from `@angular/core/testing` to `zone.js` package. But in case some user still using the old
version of `zone.js`, an old version of `fakeAsync/async` logic were still kept inside `@angular/core/testing`
package as `fallback` logic. Since now `Angular8+` already use `zone.js 0.9+`, so
those fallback logic is removed.
PR Close#37879
This partially reverts some changes from 71b9371180 (diff-dd469785fca8680a5b33b1e81c5cfd91R1420)
These broke the g3sync of zone.js because we use the output of the TypeScript compiler directly, rather than rely on the rollup commonjs plugin to define the global symbol
PR Close#31453
JiaLiPassion
Joey Perrott
Alex Eagle