Fix ordering issue of setState calls within withState

[BenSchwab]

push adds to the front of the queue, but we want to add to the end to preserve order of setState. The only time the queue will have multiple elements is within a call to withState. This is because the withState block itself will be on the background thread, so setState calls will not run immediately. Currently this test fails with the value of foo on the second call being 1 as the ordering of the setState was reversed:

 withState {
            selectSubscribe(ViewModelTestState::foo) {
                callCount++
                assertEquals(when (callCount) {
                    1 -> 0
                    2 -> 2
                    else -> throw IllegalArgumentException("Unexpected call count $callCount")
                }, it)
            }
            // These will be coalesced into one update
            setState { copy(foo = 1) }
            setState { copy(foo = 2) }
        }
        assertEquals(2, callCount)

Now it passes. Note -- that this also tests the coalescing logic of setState's within with state.

[BenSchwab]

This may be related to what was seen here: #76

[elihart]

Very nice catch, glad we have a test case for this now 👍

[gpeal]

@BenSchwab Nice!