Replace all occurrences of WITH_RUNTIME with WITH_STDLIB

We are going to deprecate `WITH_RUNTIME` directive. The main reason
behind this change is that `WITH_STDLIB` directive better describes
its meaning, specifically it will add kotlin stdlib to test's classpath.

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/canBeReplacedWithOperatorAssignment/flexibleTypeBug.kt

@@ -1,4 +1,4 @@
-// WITH_RUNTIME
+// WITH_STDLIB
 fun foo() {
     var list1 = java.util.Collections.emptyList<String>()
     val list2 = listOf("b")

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/canBeReplacedWithOperatorAssignment/list.kt

@@ -1,4 +1,4 @@
-// WITH_RUNTIME
+// WITH_STDLIB
 fun foo() {
     var list = listOf(1, 2, 3)
     // Should not be highlighted because it's the way we use to say explicitly

compiler/fir/analysis-tests/testData/resolve/extendedCheckers/canBeReplacedWithOperatorAssignment/mutableList.kt

@@ -1,4 +1,4 @@
-// WITH_RUNTIME
+// WITH_STDLIB
 
 fun foo() {
     var listVar = mutableListOf(1, 2, 3)