[AA decompiler] Store sealed modifiers in interface stubs

- If the `sealed` modifier is not kept in the interface's stub, a
  sealed interface will have an `abstract` modality instead, which
  causes issues with `when` exhaustiveness analysis in K2.
- This issue also affected K1, but it was less visible there because
  `when` exhaustiveness analysis in K1 uses deserialized descriptors.

^KT-62895

analysis/decompiled/decompiler-to-file-stubs/testData/clsFileStubBuilder/SealedInterface/SealedInterface.txt

@@ -3,7 +3,7 @@ PsiJetFileStubImpl[package=test]
     REFERENCE_EXPRESSION[referencedName=test]
   IMPORT_LIST
   CLASS[classId=test/SealedInterface, fqName=test.SealedInterface, isEnumEntry=false, isInterface=true, isLocal=false, isTopLevel=true, name=SealedInterface, superNames=[]]
-    MODIFIER_LIST[public]
+    MODIFIER_LIST[public sealed]
     CLASS_BODY
       CLASS[classId=test/SealedInterface.Nested, fqName=test.SealedInterface.Nested, isEnumEntry=false, isInterface=false, isLocal=false, isTopLevel=false, name=Nested, superNames=[SealedInterface]]
         MODIFIER_LIST[public final]

analysis/decompiled/decompiler-to-stubs/src/org/jetbrains/kotlin/analysis/decompiler/stub/ClassClsStubBuilder.kt

@@ -103,6 +103,7 @@ private class ClassClsStubBuilder(
         }
         if (isInterface()) {
             relevantFlags.add(FUN_INTERFACE)
+            relevantFlags.add(INTERFACE_MODALITY)
         }
         val additionalModifiers = when (classKind) {
             ProtoBuf.Class.Kind.ENUM_CLASS -> listOf(KtTokens.ENUM_KEYWORD)

analysis/decompiled/decompiler-to-stubs/src/org/jetbrains/kotlin/analysis/decompiler/stub/flags/flags.kt

@@ -24,6 +24,16 @@ val MODALITY: FlagsToModifiers = object : FlagsToModifiers() {
     }
 }
 
+/**
+ * For interfaces, we only need to remember a `sealed` modifier in the stub, as the interface will be abstract by default.
+ */
+val INTERFACE_MODALITY: FlagsToModifiers = object : FlagsToModifiers() {
+    override fun getModifiers(flags: Int): KtModifierKeywordToken? {
+        val modality = Flags.MODALITY.get(flags)
+        return KtTokens.SEALED_KEYWORD.takeIf { modality == ProtoBuf.Modality.SEALED }
+    }
+}
+
 val VISIBILITY: FlagsToModifiers = object : FlagsToModifiers() {
     override fun getModifiers(flags: Int): KtModifierKeywordToken? {
         val visibility = Flags.VISIBILITY.get(flags)

compiler/psi/src/org/jetbrains/kotlin/psi/stubs/KotlinStubVersions.kt

@@ -17,7 +17,7 @@ object KotlinStubVersions {
     // Binary stub version should be increased if stub format (org.jetbrains.kotlin.psi.stubs.impl) is changed
     //      or changes are made to the core stub building code (org.jetbrains.kotlin.idea.decompiler.stubBuilder).
     // Increasing this version will lead to reindexing of all binary files that are potentially kotlin binaries (including all class files).
-    private const val BINARY_STUB_VERSION = 94
+    private const val BINARY_STUB_VERSION = 95
 
     // Classfile stub version should be increased if changes are made to classfile stub building subsystem (org.jetbrains.kotlin.idea.decompiler.classFile)
     // Increasing this version will lead to reindexing of all classfiles.