Add more failure tests for adaptive executor

With #2942 we've fixed a bug, we should add more test coverage for `StartPlacementExecutionOnSession ()`. And, in general more tests needed for `MULTI_CONNECTION_LOST` case.

@metdos I assigned you because this requires some deeper dive into failure test framework. In this release, or the next, can we allocate some time to add more edge case tests via failure tests? This might require changing some code in failure test framework.