Fix type inference issues for 'if' and 'when'.

Use 'expectedType' (when present) as an explicit type argument for a special construct call.
Unfortunately, this approach can't be used for elvis due to other elvis-related inference hacks.
Fixes KT-10807, KT-10811.
This also affects KT-6189: now we can infer proper type for 'if'.

If type inference for special call failed, and we found no type errors in sub-expressions,
report TYPE_INFERENCE_FAILED_ON_SPECIAL_CONSTRUCT error.
This (and the hack above) fixes KT-10809: code no longer compiles.

compiler/testData/diagnostics/testsWithStdLib/when/kt10807.kt

@@ -0,0 +1,17 @@
+import java.util.*
+import kotlin.comparisons.compareBy
+import kotlin.comparisons.nullsLast
+
+class Foo(val a: String, val b: Int)
+
+fun getComp(): Comparator<Foo?> =
+        when {
+            else -> nullsLast(compareBy({ it.a }, { it.b }))
+        }
+
+fun getCompInverted(): Comparator<Foo?> =
+        nullsLast(
+                when {
+                    else -> compareBy({ it.a }, { it.b })
+                }
+        )