Reflection: create synthetic classes instead of throwing UOE

... for Kotlin-generated classes which do not correspond to a "class"
from the Kotlin language's point of view. For example, Kotlin lambdas,
file facade classes, multifile class facade/part classes, WhenMappings,
DefaultImpls. They can be distinguished from normal classes by the value
of `KotlinClassHeader.Kind` (which is the same as `Metadata.kind`).

Another theoretical option would be to throw exception at the point
where the `::class` expression is used, if the expression's type on the
left-hand side is a synthetic class. But we can't really do that since
it'll affect performance of most `<expression>::class` expressions.

So, construct a fake synthetic class instead, without any members except
equals/hashCode/toString, and without any non-trivial modifiers. It kind
of contradicts the general idea that kotlin-reflect presents anything
exactly the same as the compiler sees it, but arguably it's worth it to
avoid unexpected exceptions like in KT-41373.

In the newly added test, Java lambda check is muted but it should work
exactly the same as for Kotlin lambdas and other synthetic classes. It's
fixed in a subsequent commit.

 #KT-41373 In Progress

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/FirNativeCodegenBoxTestGenerated.java

@@ -36186,6 +36186,19 @@ public class FirNativeCodegenBoxTestGenerated extends AbstractNativeCodegenBoxTe
                 }
             }
 
+            @Nested
+            @TestMetadata("compiler/testData/codegen/box/reflection/syntheticClasses")
+            @TestDataPath("$PROJECT_ROOT")
+            @Tag("frontend-fir")
+            @FirPipeline()
+            @UseExtTestCaseGroupProvider()
+            public class SyntheticClasses {
+                @Test
+                public void testAllFilesPresentInSyntheticClasses() throws Exception {
+                    KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/reflection/syntheticClasses"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.NATIVE, true);
+                }
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/reflection/typeOf")
             @TestDataPath("$PROJECT_ROOT")

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/FirNativeCodegenBoxTestNoPLGenerated.java

@@ -37102,6 +37102,21 @@ public class FirNativeCodegenBoxTestNoPLGenerated extends AbstractNativeCodegenB
                 }
             }
 
+            @Nested
+            @TestMetadata("compiler/testData/codegen/box/reflection/syntheticClasses")
+            @TestDataPath("$PROJECT_ROOT")
+            @Tag("frontend-fir")
+            @FirPipeline()
+            @UseExtTestCaseGroupProvider()
+            @UsePartialLinkage(mode = Mode.DISABLED)
+            @Tag("no-partial-linkage-may-be-skipped")
+            public class SyntheticClasses {
+                @Test
+                public void testAllFilesPresentInSyntheticClasses() throws Exception {
+                    KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/reflection/syntheticClasses"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.NATIVE, true);
+                }
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/reflection/typeOf")
             @TestDataPath("$PROJECT_ROOT")

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/NativeCodegenBoxTestGenerated.java

@@ -35729,6 +35729,18 @@ public class NativeCodegenBoxTestGenerated extends AbstractNativeCodegenBoxTest
                 }
             }
 
+            @Nested
+            @TestMetadata("compiler/testData/codegen/box/reflection/syntheticClasses")
+            @TestDataPath("$PROJECT_ROOT")
+            @UseExtTestCaseGroupProvider()
+            @DisabledTestsIfProperty(sourceLocations = { "compiler/testData/codegen/box/coroutines/featureIntersection/defaultExpect.kt", "compiler/testData/codegen/box/multiplatform/defaultArguments/*.kt", "compiler/testData/codegen/box/multiplatform/migratedOldTests/*.kt", "compiler/testData/codegen/boxInline/multiplatform/defaultArguments/receiversAndParametersInLambda.kt" }, property = ClassLevelProperty.TEST_MODE, propertyValue = "ONE_STAGE_MULTI_MODULE")
+            public class SyntheticClasses {
+                @Test
+                public void testAllFilesPresentInSyntheticClasses() throws Exception {
+                    KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/reflection/syntheticClasses"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.NATIVE, true);
+                }
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/reflection/typeOf")
             @TestDataPath("$PROJECT_ROOT")

native/native.tests/tests-gen/org/jetbrains/kotlin/konan/blackboxtest/NativeCodegenBoxTestNoPLGenerated.java

@@ -36187,6 +36187,19 @@ public class NativeCodegenBoxTestNoPLGenerated extends AbstractNativeCodegenBoxT
                 }
             }
 
+            @Nested
+            @TestMetadata("compiler/testData/codegen/box/reflection/syntheticClasses")
+            @TestDataPath("$PROJECT_ROOT")
+            @UseExtTestCaseGroupProvider()
+            @UsePartialLinkage(mode = Mode.DISABLED)
+            @Tag("no-partial-linkage-may-be-skipped")
+            public class SyntheticClasses {
+                @Test
+                public void testAllFilesPresentInSyntheticClasses() throws Exception {
+                    KtTestUtil.assertAllTestsPresentByMetadataWithExcluded(this.getClass(), new File("compiler/testData/codegen/box/reflection/syntheticClasses"), Pattern.compile("^(.+)\\.kt$"), null, TargetBackend.NATIVE, true);
+                }
+            }
+
             @Nested
             @TestMetadata("compiler/testData/codegen/box/reflection/typeOf")
             @TestDataPath("$PROJECT_ROOT")