Split ReplaceSingleLineLetInspection to SimpleRedundantLet & ComplexRedundantLet

Relates to #KT-32010

idea/testData/inspectionsLocal/simpleRedundantLet/lambdaWithBinaryExpression2.kt

@@ -0,0 +1,6 @@
+// WITH_RUNTIME
+// PROBLEM: none
+
+fun baz(foo: String) {
+    foo.let<caret> { it.length + "".indexOfLast { c -> c == it[0] } }
+}