Migrate compiler, idea and others to new case conversion api

compiler/psi/src/org/jetbrains/kotlin/parsing/ParseUtils.kt

@@ -79,7 +79,7 @@ private fun parseLong(text: String): Long? {
 }
 
 private fun parseFloatingLiteral(text: String): Number? {
-    if (text.toLowerCase().endsWith('f')) {
+    if (text.lowercase().endsWith('f')) {
         return parseFloat(text)
     }
     return parseDouble(text)

compiler/psi/src/org/jetbrains/kotlin/psi/stubs/impl/KotlinStubBaseImpl.kt

@@ -72,7 +72,7 @@ open class KotlinStubBaseImpl<T : KtElementImplStub<*>>(parent: StubElement<*>?,
     private fun getPropertyName(method: Method): String {
         val methodName = method.name!!
         if (methodName.startsWith("get")) {
-            return methodName.substring(3).decapitalize()
+            return methodName.substring(3).replaceFirstChar(Char::lowercaseChar)
         }
         return methodName
     }