JVM IR: fix flags of $default methods in multi-file facades

Do not change origin of multifile class bridges to something else
because, as it turns out, there are numerous origin-specific checks in
the codegen that start to behave differently for multifile bridges.
Instead of the method-targeted origin MULTIFILE_BRIDGE, use new class
origin JVM_MULTIFILE_CLASS to detect whether a declaration is a
multifile bridge.

 #KT-40198 Fixed
 #KT-43145 Fixed

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/declarations/IrDeclarationOrigin.kt

@@ -38,6 +38,8 @@ interface IrDeclarationOrigin {
 
     object FILE_CLASS : IrDeclarationOriginImpl("FILE_CLASS")
     object SYNTHETIC_FILE_CLASS : IrDeclarationOriginImpl("SYNTHETIC_FILE_CLASS", isSynthetic = true)
+    object JVM_MULTIFILE_CLASS : IrDeclarationOriginImpl("JVM_MULTIFILE_CLASS")
+
     object SCRIPT_CLASS : IrDeclarationOriginImpl("SCRIPT_CLASS")
     object SCRIPT_STATEMENT : IrDeclarationOriginImpl("SCRIPT_STATEMENT")
     object SCRIPT_CALL_PARAMETER : IrDeclarationOriginImpl("SCRIPT_CALL_PARAMETER")

compiler/ir/ir.tree/src/org/jetbrains/kotlin/ir/util/IrUtils.kt

@@ -529,7 +529,10 @@ val IrFunctionAccessExpression.typeSubstitutionMap: Map<IrTypeParameterSymbol, I
     get() = getTypeSubstitutionMap(symbol.owner)
 
 val IrDeclaration.isFileClass: Boolean
-    get() = origin == IrDeclarationOrigin.FILE_CLASS || origin == IrDeclarationOrigin.SYNTHETIC_FILE_CLASS
+    get() =
+        origin == IrDeclarationOrigin.FILE_CLASS ||
+                origin == IrDeclarationOrigin.SYNTHETIC_FILE_CLASS ||
+                origin == IrDeclarationOrigin.JVM_MULTIFILE_CLASS
 
 val IrValueDeclaration.isImmutable: Boolean
     get() = this is IrValueParameter || this is IrVariable && !isVar