Dependent streams should end when their parent ends

Expected Behavior

const s = Stream()
const c = stream.map(a => a)
s.end.map(() => console.log('parent ended'))
c.end.map(() => console.log('child ended'))
stream.end(true) // logs "parent ended" and "child ended"

Current Behavior

const s = Stream()
const c = stream.map(a => a)
s.end.map(() => console.log('parent ended'))
c.end.map(() => console.log('child ended'))
stream.end(true) // logs just "parent ended"

Possible Solution

Potentially something down the vein of this comment by @pygy, but it may need altered.

Context

I created this issue to track the issue reported in #2030 (a heavily outdated PR targeting the wrong branch).

Start by tracing the stream behavior shown in the expected and current examples, then read the discussion linked from issue #2030 and its referenced pull request comment. Done means ending the parent stream also triggers the child stream's end notification, while preserving the parent notification.