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/sealedClass_else.kt

@@ -0,0 +1,10 @@
+sealed class Foo {
+    object A : Foo()
+    class B(val i: Int) : Foo()
+}
+
+fun test(e: Foo) {
+    <caret>when (e) {
+        else -> {}
+    }
+}