FIR: Fix incorrectly serialized type

See the test added: there's a non-denotable T!! type inside flexible type
that wasn't handled before.

ConeKotlinType::contains handles flexible types content and some other cases
Also, it has better asymptotics

plugins/kapt3/kapt3-compiler/test/org/jetbrains/kotlin/kapt3/test/ClassFileToSourceStubConverterTestGenerated.java

@@ -74,7 +74,6 @@ public class ClassFileToSourceStubConverterTestGenerated extends AbstractClassFi
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/comments.kt");
     }
 
-    /** Regression test for KT-43593. */
     @TestMetadata("commentsRemoved.kt")
     public void testCommentsRemoved() throws Exception {
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/commentsRemoved.kt");

plugins/kapt3/kapt3-compiler/test/org/jetbrains/kotlin/kapt3/test/IrClassFileToSourceStubConverterTestGenerated.java

@@ -75,7 +75,6 @@ public class IrClassFileToSourceStubConverterTestGenerated extends AbstractIrCla
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/comments.kt");
     }
 
-    /** Regression test for KT-43593. */
     @TestMetadata("commentsRemoved.kt")
     public void testCommentsRemoved() throws Exception {
         runTest("plugins/kapt3/kapt3-compiler/testData/converter/commentsRemoved.kt");