Should EventStream.delay accept the event arg by-name?

[raquo]

• EventStream.delay(100, ev) should not evaluate ev until after 100ms have passed.
• ev should be re-evaluated every time the stream starts, unless emitOnce = true is set (then subsequent starts don't emit anything, same as now)

This would make EventStream.delay(ms, ev) behave the same as EventStream.delay(ms).mapTo(ev) rather than EventStream(ev).delay(ms).

(Note: EventStream.apply is the future alias to EventStream.fromValue, not yet available)

I don't know, maybe we should even remove the ability to pass ev to EventStream.delay at all, to force users to clarify their intent. With the new apply alias, both options will become quite ergonomic to write.