message: Fix some spots where tests accidentally copied TestFiles instead of Realm::Configs
  This was causing some spurious unlink() failures when running the tests on
  Windows.
diff: @@ -2517,12 +2517,12 @@ TEST_CASE("migration: AdditiveDiscovered") {
  }
  DYNAMIC_SECTION("can have different subsets of columns in different Realm instances" << mode_string) {
  - auto config2 = config;
  + Realm::Config config2 = config;
  config2.schema = add_property(schema, "object", {"value 3", PropertyType::Int});
  - auto config3 = config;
  + Realm::Config config3 = config;
  config3.schema = remove_property(schema, "object", "value 2");
  - auto config4 = config;
  + Realm::Config config4 = config;
  config4.schema = util::none;
  auto realm2 = Realm::get_shared_realm(config2);
  @@ -2542,7 +2542,7 @@ TEST_CASE("migration: AdditiveDiscovered") {
  }
  DYNAMIC_SECTION("updating a schema to include already-present column" << mode_string) {
  - auto config2 = config;
  + Realm::Config config2 = config;
  config2.schema = add_property(schema, "object", {"value 3", PropertyType::Int});
  auto realm2 = Realm::get_shared_realm(config2);
  auto& properties2 = realm2->schema().find("object")->persisted_properties;
  @@ -2567,14 +2567,14 @@ TEST_CASE("migration: AdditiveDiscovered") {
  Schema schema1 = realm1->schema();
  realm1->close();
  - auto config2 = config1;
  + Realm::Config config2 = config1;
  config2.schema_version = 1;
  auto realm2 = Realm::get_shared_realm(config2);
  REQUIRE(realm2->schema() == schema1);
  }
  DYNAMIC_SECTION("invalid schema update leaves the schema untouched" << mode_string) {
  - auto config2 = config;
  + Realm::Config config2 = config;
  config2.schema = add_property(schema, "object", {"value 3", PropertyType::Int});
  auto realm2 = Realm::get_shared_realm(config2);
  