Wrap with let: apply to unsafe qualified expression

#KT-18125 Fixed

idea/testData/quickfix/wrapWithSafeLetCall/unsafe.kt

@@ -0,0 +1,7 @@
+// "Wrap with '?.let { ... }' call" "true"
+// WITH_RUNTIME
+fun foo(s: String) {}
+
+fun bar(s: String?) {
+    foo(s<caret>.substring(1))
+}

idea/testData/quickfix/wrapWithSafeLetCall/unsafe.kt.after

@@ -0,0 +1,7 @@
+// "Wrap with '?.let { ... }' call" "true"
+// WITH_RUNTIME
+fun foo(s: String) {}
+
+fun bar(s: String?) {
+    s?.let { foo(it.substring(1)) }
+}

idea/testData/quickfix/wrapWithSafeLetCall/unsafe2.kt

@@ -0,0 +1,13 @@
+// "Wrap with '?.let { ... }' call" "true"
+// WITH_RUNTIME
+class A(val b: B)
+class B {
+    fun c(s: String) {}
+}
+
+class X(val y: Y)
+class Y(val z: String)
+
+fun test(a: A, x: X?) {
+    a.b.c(x?.y<caret>.z)
+}

idea/testData/quickfix/wrapWithSafeLetCall/unsafe2.kt.after

@@ -0,0 +1,13 @@
+// "Wrap with '?.let { ... }' call" "true"
+// WITH_RUNTIME
+class A(val b: B)
+class B {
+    fun c(s: String) {}
+}
+
+class X(val y: Y)
+class Y(val z: String)
+
+fun test(a: A, x: X?) {
+    x?.y?.let { a.b.c(it.z) }
+}

idea/testData/quickfix/wrapWithSafeLetCall/unsafeForNullableParameter.kt

@@ -0,0 +1,12 @@
+// "Wrap with '?.let { ... }' call" "false"
+// ACTION: Add 's =' to argument
+// ACTION: Add non-null asserted (!!) call
+// ACTION: Replace with safe (?.) call
+// ACTION: Surround with null check
+// DISABLE-ERRORS
+// WITH_RUNTIME
+fun foo(s: String?) {}
+
+fun bar(s: String?) {
+    foo(s<caret>.substring(1))
+}