Rename isImpl to isActual in descriptors

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/DeepCopyIrTreeWithDescriptoros.kt

@@ -278,7 +278,7 @@ class DeepCopyIrTreeWithDescriptors(val targetDescriptor: FunctionDescriptor,
                 /* lateInit              = */ oldDescriptor.isLateInit,
                 /* isConst               = */ oldDescriptor.isConst,
                 /* isExpect              = */ oldDescriptor.isExpect,
-                /* isImpl                = */ oldDescriptor.isImpl,
+                /* isActual                = */ oldDescriptor.isActual,
                 /* isExternal            = */ oldDescriptor.isExternal,
                 /* isDelegated           = */ oldDescriptor.isDelegated
             ).apply {

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/IrBuildUtils.kt

@@ -179,7 +179,7 @@ fun BackendContext.createPropertyWithBackingFieldBuilder(startOffset: Int, endOf
                     /* lateInit              = */ false,
                     /* isConst               = */ false,
                     /* isExpect              = */ false,
-                    /* isImpl                = */ false,
+                    /* isActual                = */ false,
                     /* isExternal            = */ false,
                     /* isDelegated           = */ false
             )

compiler/ir/backend.common/src/org/jetbrains/kotlin/backend/common/lower/LocalDeclarationsLowering.kt

@@ -598,7 +598,7 @@ class LocalDeclarationsLowering(val context: BackendContext) : DeclarationContai
                         /* lateInit = */ false,
                         /* isConst = */ false,
                         /* isExpect = */ false,
-                        /* isImpl = */ false,
+                        /* isActual = */ false,
                         /* isExternal = */ false,
                         /* isDelegated = */ false)