Because the is "end glow" is when a hyper-dash is *started*, the name was confusing.
The "after-image" was already used in the code as a synonym of "end glow" inconsistently.
It resolves mutual dependency of `Catcher` and `CatcherTrailDisplay`.
Trail generation logic is moved to `Catcher`.
The generation logic no longer uses delayed scheduling because the hidden state is hard to manage.
Instead, the last time a trail is generated is calculated and used.
The new logic has a different behavior when the dash key is pressed in succession under 50ms, but it is not noticeable for normal plays.
