Simplify coroutine generation in JS backend

Stop making aliasing suspend function descriptor with reference to
instance of state machine. This may cause problems in some cases,
for example, when compiling recursive suspend function. See KT-17281.
Instead, make alias for synthetic continuation parameter. This
additionally required some refactoring, e.g. *always* generating
continuation parameter during codegen.

compiler/testData/codegen/box/coroutines/recursiveSuspend.kt

@@ -0,0 +1,42 @@
+// IGNORE_BACKEND: NATIVE
+// WITH_RUNTIME
+// WITH_COROUTINES
+import kotlin.coroutines.experimental.*
+import kotlin.coroutines.experimental.intrinsics.*
+
+fun box(): String {
+    var result = 0
+
+    builder {
+        result = factorial(4)
+    }
+
+    while (postponed != null) {
+        postponed!!()
+    }
+
+    if (result != 24) return "fail1: $result"
+    if (log != "1;1;2;6;24;") return "fail2: $log"
+
+    return "OK"
+}
+
+suspend fun factorial(a: Int): Int = if (a > 0) suspendHere(factorial(a - 1) * a) else suspendHere(1)
+
+suspend fun suspendHere(value: Int): Int = suspendCoroutineOrReturn { x ->
+    postponed = {
+        log += "$value;"
+        x.resume(value)
+    }
+    COROUTINE_SUSPENDED
+}
+
+fun builder(c: suspend () -> Unit) {
+    c.startCoroutine(handleResultContinuation {
+        postponed = null
+    })
+}
+
+var postponed: (() -> Unit)? = { }
+
+var log = ""