In 5c547675b11a24b16c20df1718583a0e7ed49cbd the `EventEmitter.subscribe`
API was extended with a new signature that allows the emitter's generic
type `T` to flow into the subscribe callback. This new signature removes
the need for the special `_outputHelper` function that used to be
emitted into TCBs when `strictOutputEventTypes`/`strictTemplates` is
enabled.
PR Close#40738