Raise error from Cucumber Queue Mode runner when system process doesn't finish execution

[shadre]

Problem

Sometimes Cucumber in Queue Mode could be killed by CI server for some reason (like exceeding the memory).
We want to make sure the user gets meaningful error as to what happened (and be double sure that killing the process never results in a false positive).

Fix

We raise exception when Cucumber process in Queue Mode failed to execute properly (never exited on its own).

[ArturT]

We can add some context in the description of this PR like. This can be useful if someone will check this PR to understand why we did the change.

# Problem

example edge case when Cucumber can be killed by CI. Explain that this could lead to situation that tests was green but never run due to Cucumber process killed.

# Fix

We raise exception when Cucumber process was killed.