Having brought back an explicit interface for `throttle`
[here](https://github.com/pointfreeco/swift-composable-architecture/pull/2368)
we should also consider providing an explicit interface for `debounce`.
Though a clock-based debounce is a matter of:
```swift
return .run { send in
try await withTaskCancellation(id: CancelID.debounce) {
try await clock.sleep(for: .seconds(1))
await send(.action)
}
}
```
A dedicated operator simplifies and flattens:
```swift
return .send(.action)
.debounce(id: CancelID.debounce, for: .seconds(1), clock: clock)
```
This PR only brings back the scheduler-based API, so alongside #2368 we
are reintroducing two Combine-forward APIs for this work. Before
we release a 1.1 that fully commits these APIs, we should consider if we
can make clock-based APIs work, instead (or in addition). If in
addition, we should also consider introducing the Combine-based APIs as
soft-deprecated to begin with.
