Multiple suspension points support

[avpotapov00]

Closes #122

[eupp]

We discussed this PR today with @avpotapov00 , and come to the conclusion that it overlaps with #361.

This PR implements three things:

1. Fix for events tracking in a resumption part of a coroutine.
2. Fix for the trace collection in a resumption part of a coroutine.
3. Multiple suspension points support.

Independently, while working on the new model checking strategy, I also discovered problems (1) and (2), and opened PR #361.

At first I was only aware that this PR fixes (1), so I borrowed the relevant code in the commit ab760ef.

Then I independently developed different fix for (2).
As we discussed today, this fix also handles more complicated case, when the resumed part of the coroutine has several nested suspend functions. To handle this case, I save the stack of suspended functions, and then restore it on resumption.

So after the discussion, we thought that it would be good idea to split this PR into two parts.

1. The first part should contain fixes for problems (1) and (2), and will be delivered under Fix resumption trace collection and printing logic #361
2. The second part should contain the multiple suspension points logic, and should be delivered after the first part.