In #41995 the type of `TrackByFunction` was changed such that the
declaration of a `trackBy` function did not cause the item type to be
widened to the `trackBy`'s item type, which may be a supertype of the
iterated type. This has introduced situations where the template type
checker is now reporting errors for cases where a `trackBy` function is
no longer assignable to `TrackByFunction`.
This commit fixes the error by also including the item type `T` in
addition to the constrained type parameter `U`, allowing TypeScript to
infer an appropriate `T`.
Fixes#42609
PR Close#42692
Given we have updated API extractor to the most recent
version, we need to update the API goldens because the
latest version uses alias exports to avoid collisions with
default library globals (like `Event`).
PR Close#42737