Adapt WHEN_WITHOUT_ELSE according to new features of Kotlin 1.6

[petertrr]

Now our 'generated else block' is treated as a compiler warning sometimes:

when (state.confirmationType) {
                ConfirmationType.NO_BINARY_CONFIRM, ConfirmationType.NO_CONFIRM -> submitExecutionRequest()
                ConfirmationType.DELETE_CONFIRM -> deleteProjectBuilder()
                else -> {
                    // this is a generated else block
                }
            }

causes

w: 'when' is exhaustive so 'else' is redundant here

[sanyavertolet]

I am not sure if it is possible to tell whether else block is redundant or not without compiling.
In example above ConfirmationType could be declared in another file so if we examine the only file with an example we cannot see if when covers all possible values of `ConfirmationType'.

[petertrr]

I think this can be considered similar to #1168 : we don't have enough information to reason about when statement, so we just skip it and let the user use compiler warnings. We can detect if all branches are enum entries (e.g. there are no call statements or literals) and skip these cases.