This commit introduces the `output()` function and corresponding
runtime code.
In practice, `output()` will defer to `EventEmitter` as outlined in the
RFC, but we are considering limiting the type to a minimal version that
is not coupled with RxJS, less complex, and also has better type safety
around emitting of values.
E.g. currently `EventEmitter.emit` can always be called without
any value, even though the output may be typed to always pass around
values of type `T`. This could cause subtle and confusing bugs.
PR Close#54217
Paul Gschwendtner
c05e1042b4