Split ReplaceSingleLineLetInspection to SimpleRedundantLet & ComplexRedundantLet

Relates to #KT-32010

idea/testData/inspectionsLocal/complexRedundantLet/functionInVariableInvokeCall.kt

@@ -0,0 +1,7 @@
+// PROBLEM: none
+// WITH_RUNTIME
+class Foo(val bar: () -> Int)
+
+fun bar(foo: Foo?) {
+    foo?.<caret>let { it.bar.invoke() }
+}