Allow return statements in secondary constructors

compiler/testData/diagnostics/tests/secondaryConstructors/return.kt

@@ -0,0 +1,17 @@
+
+class A {
+    init {
+        <!RETURN_NOT_ALLOWED!>return<!>
+        <!RETURN_NOT_ALLOWED!>return 1<!>
+    }
+    constructor() {
+        if (1 == 1) {
+            return
+            return <!CONSTANT_EXPECTED_TYPE_MISMATCH!>1<!>
+        }
+        return
+        return <!TYPE_MISMATCH!>foo()<!>
+    }
+
+    fun foo(): Int = 1
+}

compiler/testData/diagnostics/tests/secondaryConstructors/return.txt

@@ -0,0 +1,9 @@
+package
+
+internal final class A {
+    public constructor A()
+    public open override /*1*/ /*fake_override*/ fun equals(/*0*/ other: kotlin.Any?): kotlin.Boolean
+    internal final fun foo(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun hashCode(): kotlin.Int
+    public open override /*1*/ /*fake_override*/ fun toString(): kotlin.String
+}