IC: Small cleanup in KotlinClassInfo.kt

This is to address the not-yet-resolved comments in
https://github.com/JetBrains/kotlin/pull/5127, plus a few other small
(non-functional) changes.

^KT-58986: In progress

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/classpathDiff/ClasspathChangesComputerTest.kt

@@ -261,7 +261,7 @@ class KotlinOnlyClasspathChangesComputerTest : ClasspathChangesComputerTest() {
     fun testRenameFileFacade() {
         // Check that classpath changes computation doesn't fail.
         // Ideally, the returned changes should be empty (renaming a file facade alone shouldn't cause any `LookupSymbol`s to change), but
-        // it is currently not the case. However, this is just a small efficiency, not a serious bug.
+        // it is currently not the case. However, this is just a small inefficiency, not an IC-correctness bug.
         val changes = computeClasspathChanges(File(testDataDir, "KotlinOnly/testRenameFileFacade/src"), tmpDir)
         Changes(
             lookupSymbols = setOf(
@@ -275,6 +275,10 @@ class KotlinOnlyClasspathChangesComputerTest : ClasspathChangesComputerTest() {
     /** Regression test for KT-58289.*/
     @Test
     fun testChangedAnnotations() {
+        // Note: Currently we detect changes to annotations on Kotlin classes, but not annotations on properties and functions, so the
+        // following changes are missing: `SomeClass.propertyWithChangedAnnotation` and `SomeClass.functionWithChangedAnnotation`.
+        // Once all annotations are added to Kotlin metadata (KT-57919), we should be able to detect changes to them (i.e., we'll need to
+        // update this test assertion then).
         val changes = computeClasspathChanges(File(testDataDir, "KotlinOnly/testChangedAnnotations/src"), tmpDir)
         Changes(
             lookupSymbols = setOf(

compiler/incremental-compilation-impl/test/org/jetbrains/kotlin/incremental/classpathDiff/ClasspathSnapshotTestCommon.kt

@@ -138,6 +138,8 @@ abstract class ClasspathSnapshotTestCommon {
                 "-classpath", (listOf(srcDir) + classpath).joinToString(File.pathSeparator) { it.path }
             )
             runCommandInNewProcess(commandAndArgs)
+
+            classesDir.resolve("META-INF").deleteRecursively()
         }
 
         private fun compileJava(srcDir: File, classesDir: File, classpath: List<File>): List<ClassFile> {