Join declaration & assignment is no more suggested in case of potential smart cast available #KT-15412 Fixed

idea/testData/intentions/joinDeclarationAndAssignment/assignmentForFlexible.kt

@@ -0,0 +1,6 @@
+// IS_APPLICABLE: true
+// WITH_RUNTIME
+fun foo() {
+    val x: String<caret>
+    x = System.getProperty("")
+}

idea/testData/intentions/joinDeclarationAndAssignment/assignmentForFlexible.kt.after

@@ -0,0 +1,5 @@
+// IS_APPLICABLE: true
+// WITH_RUNTIME
+fun foo() {
+    val x: String = System.getProperty("")
+}

idea/testData/intentions/joinDeclarationAndAssignment/assignmentForSmartCast.kt

@@ -0,0 +1,6 @@
+// IS_APPLICABLE: false
+fun foo() {
+    val x: Any<caret>
+    x = "123"
+    x.length // Smart cast before join, error after join
+}