fix: ensure Topic#publish1 returns accurate result during concurrent closure

[guptapratykshh]

this pr ensures Topic#publish1 accurately returns Left(Closed) when delivery fails due to concurrent topic closure by checking individual subscriber channel results and also guarantees that Right(()) response from publish1 consistently signifies successful delivery to all currently registered subscribers.

Resolves #3644

[guptapratykshh]

@mpilquist can you have a look at this PR , Thanks.

[mpilquist]

Need to rebase this PR now that other PRs have been merged. Also, need to remove the .fail from this test case: #3645

[mpilquist]

@TomasMikula Mind reviewing this PR? Thanks!

[TomasMikula]

So this PR guarantees that

• if publish1 returns Right(()), then all subscribers receive the event

whereas the failing test also requires that

• if publish1 returns Left(Closed), then no subscribers receive the event.

I admit the test is somewhat strict, and I'd consider the implemented behavior acceptable if clearly documented that return value Left(Closed) admits some subscribers receiving the event anyway.

[TomasMikula]

Minor thing: I think constructing the effect in a right-associative way will lead to slightly faster execution for an IO-like F.

[TomasMikula]

@guptapratykshh So you went full on to satisfy the test as is (as opposed to relaxing the test as suggested above).

My main concern with this implementation is that

• publish1 is now uncancelable (via Ref's flatModify)
• close, which was already uncancelable, now waits for publishers to finish.

These might be breaking changes for existing users.