Fix TriggerEvent problem with iterate breaking on Remove when it has multiple handlers

[hadashiA]

After merging #445 , TriggerEvent test was broken... 🙏

Problem:

• In h.Next, In the loop of TriggerEvent.SetResult
  • if Remove(h.Next), next is unreliable.
• Also, .SetCompleted , .SetError, .SetCancelled needs to be similar fixes.

Fix:

• If it removes itself, iteratingNode instance variable is rewritten to refer to iteratingNode instead of h.Next.

[hadashiA]

📝
Oh..., it looks like Linq/PublishTest is hunging up.
I'd like to revert #445 once, as it seems like it would be a pain to fix right away..

Reverted: #488

[hadashiA]

I found the cause, merged #445 and added more fixes. The test passed.

[neuecc]

hope to work correctly:)