Support 'break' and 'continue' in expressions

- generate fake jump instructions so that we can always analyze stack depths
- fix stack before break and continue by dropping excessive elements (e.g., *a*.foo(*b*, c?:continue))
- Analyzer rewritten in Kotlin, with more flexible control of CFG traversal

 #Fixed KT-3340
 #Fixed KT-4258
 #Fixed KT-7941

compiler/testData/codegen/boxWithStdlib/controlStructures/continueInExpr.kt

@@ -0,0 +1,14 @@
+fun concatNonNulls(strings: List<String?>): String {
+    var result = ""
+    for (str in strings) {
+        result += str?:continue
+    }
+    return result
+}
+
+fun box(): String {
+    val test = concatNonNulls(listOf("abc", null, null, "", null, "def"))
+    if (test != "abcdef") return "Failed: test=$test"
+
+    return "OK"
+}