Analysis API: add test covering get missing when branches

Also fix FIR implementation to generate boolean branches in the same
order as FE1.0.

analysis/analysis-api/testData/components/whenMissingCases/enum_partial.kt

@@ -0,0 +1,9 @@
+enum class MyEnum {
+    A, B, C
+}
+
+fun test(e: MyEnum) {
+    <caret>when (e) {
+        MyEnum.A -> {}
+    }
+}