Write proto flag about compatibility mode

There is no any special aim for this flag now.
  But it could be useful in future in case of compatibility mode deprecation

compiler/backend/src/org/jetbrains/kotlin/codegen/serialization/JvmSerializerExtension.kt

@@ -94,7 +94,13 @@ class JvmSerializerExtension @JvmOverloads constructor(
         writeVersionRequirementForJvmDefaultIfNeeded(descriptor, proto, versionRequirementTable)
 
         if (jvmDefaultMode.forAllMethodsWithBody && isInterface(descriptor)) {
-            proto.setExtension(JvmProtoBuf.jvmClassFlags, JvmFlags.getClassFlags(true))
+            proto.setExtension(
+                JvmProtoBuf.jvmClassFlags,
+                JvmFlags.getClassFlags(
+                    jvmDefaultMode.forAllMethodsWithBody,
+                    JvmDefaultMode.ALL_COMPATIBILITY == jvmDefaultMode
+                )
+            )
         }
     }
 

compiler/fir/fir2ir/jvm-backend/src/org/jetbrains/kotlin/fir/backend/jvm/FirJvmSerializerExtension.kt

@@ -95,7 +95,13 @@ class FirJvmSerializerExtension @JvmOverloads constructor(
         writeVersionRequirementForJvmDefaultIfNeeded(klass, proto, versionRequirementTable)
 
         if (jvmDefaultMode.forAllMethodsWithBody && klass is FirRegularClass && klass.classKind == ClassKind.INTERFACE) {
-            proto.setExtension(JvmProtoBuf.jvmClassFlags, JvmFlags.getClassFlags(true))
+            proto.setExtension(
+                JvmProtoBuf.jvmClassFlags,
+                JvmFlags.getClassFlags(
+                    jvmDefaultMode.forAllMethodsWithBody,
+                    JvmDefaultMode.ALL_COMPATIBILITY == jvmDefaultMode
+                )
+            )
         }
     }
 

core/metadata.jvm/src/jvm_metadata.proto

@@ -129,7 +129,8 @@ extend Class {
   optional int32 anonymous_object_origin_name = 103 [(string_id_in_table) = true];
 
 
-  // isFunctionBodyInInterface: 0 if actual body generated in DefaultImpl, 1 - otherwise (in interface default method)
+  // first bit: isFunctionBodyInInterface: 0 if actual body generated in DefaultImpl, 1 - otherwise (in interface default method)
+  // second bit: is all-compatibility mode or not, 1 - yes, 0 - no
   optional int32 jvm_class_flags = 104 [default = 0];
 }
 

core/metadata.jvm/src/org/jetbrains/kotlin/metadata/jvm/deserialization/JvmFlags.kt

@@ -16,11 +16,12 @@ object JvmFlags {
 
     //Class
     val ARE_INTERFACE_METHOD_BODIES_INSIDE = Flags.FlagField.booleanFirst()
+    val IS_ALL_COMPATIBILITY_MODE = Flags.FlagField.booleanAfter(ARE_INTERFACE_METHOD_BODIES_INSIDE)
 
     fun getPropertyFlags(isMovedFromInterfaceCompanion: Boolean): Int =
         IS_MOVED_FROM_INTERFACE_COMPANION.toFlags(isMovedFromInterfaceCompanion)
 
-    fun getClassFlags(isAllInterfaceBodiesInside: Boolean): Int =
-        ARE_INTERFACE_METHOD_BODIES_INSIDE.toFlags(isAllInterfaceBodiesInside)
+    fun getClassFlags(isAllInterfaceBodiesInside: Boolean, isAllCompatibilityMode: Boolean): Int =
+        ARE_INTERFACE_METHOD_BODIES_INSIDE.toFlags(isAllInterfaceBodiesInside) or IS_ALL_COMPATIBILITY_MODE.toFlags(isAllCompatibilityMode)
 
 }