Improve toString of platform types created by typeOf

In the stdlib implementation, render "!" if the type is only
nullability-flexible. Otherwise, render "($lower..$upper)".

Note that full kotlin-reflect has a much more complicated logic (see
`DescriptorRendererImpl.renderFlexibleType`) that renders things like
`(Mutable)List` and so on. It is not a goal of the stdlib implementation
to replicate all of that, since it requires copying a large amount of
code, namely the entirety of `JavaToKotlinClassMap` to map Java class
names to Kotlin.

compiler/tests-gen/org/jetbrains/kotlin/codegen/LightAnalysisModeTestGenerated.java

@@ -29840,6 +29840,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                 runTest("compiler/testData/codegen/box/reflection/typeOf/nothing_before.kt");
             }
 
+            @TestMetadata("primitiveJavaTypes.kt")
+            public void testPrimitiveJavaTypes() throws Exception {
+                runTest("compiler/testData/codegen/box/reflection/typeOf/primitiveJavaTypes.kt");
+            }
+
             @TestMetadata("rawTypes_after.kt")
             public void testRawTypes_after() throws Exception {
                 runTest("compiler/testData/codegen/box/reflection/typeOf/rawTypes_after.kt");
@@ -29920,6 +29925,11 @@ public class LightAnalysisModeTestGenerated extends AbstractLightAnalysisModeTes
                     runTest("compiler/testData/codegen/box/reflection/typeOf/noReflect/nothing_before.kt");
                 }
 
+                @TestMetadata("primitiveJavaTypes.kt")
+                public void testPrimitiveJavaTypes() throws Exception {
+                    runTest("compiler/testData/codegen/box/reflection/typeOf/noReflect/primitiveJavaTypes.kt");
+                }
+
                 @TestMetadata("rawTypes_after.kt")
                 public void testRawTypes_after() throws Exception {
                     runTest("compiler/testData/codegen/box/reflection/typeOf/noReflect/rawTypes_after.kt");