Extract Function: Fix type candidates for parameters with flexibly nullable types

#KT-6546 Fixed

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithNull.kt

@@ -0,0 +1,7 @@
+// WITH_RUNTIME
+// PARAM_TYPES: String?, String, kotlin.CharSequence?, CharSequence
+// PARAM_DESCRIPTOR: val property: (String..String?) defined in test
+fun test() {
+    val property = System.getProperty("some")
+    val n = <selection>property?.length()</selection>
+}

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithNull.kt.after

@@ -0,0 +1,11 @@
+// WITH_RUNTIME
+// PARAM_TYPES: String?, String, kotlin.CharSequence?, CharSequence
+// PARAM_DESCRIPTOR: val property: (String..String?) defined in test
+fun test() {
+    val property = System.getProperty("some")
+    val n = i(property)
+}
+
+private fun i(property: String?): Int? {
+    return property?.length()
+}

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithoutNull.kt

@@ -0,0 +1,7 @@
+// WITH_RUNTIME
+// PARAM_TYPES: String, CharSequence
+// PARAM_DESCRIPTOR: val property: (String..String?) defined in test
+fun test() {
+    val property = System.getProperty("some")
+    val n = <selection>property.length()</selection>
+}

idea/testData/refactoring/extractFunction/parameters/candidateTypes/flexibleTypesWithoutNull.kt.after

@@ -0,0 +1,11 @@
+// WITH_RUNTIME
+// PARAM_TYPES: String, CharSequence
+// PARAM_DESCRIPTOR: val property: (String..String?) defined in test
+fun test() {
+    val property = System.getProperty("some")
+    val n = i(property)
+}
+
+private fun i(property: String): Int {
+    return property.length()
+}