Address failure test_rename_column_with_multi_column_index with Oracle

This pull request addresses this failure.

```ruby
$ ARCONN=oracle ruby -Itest test/cases/migration/columns_test.rb -n test_rename_column_with_multi_column_indexUsing oracle
Run options: -n test_rename_column_with_multi_column_index --seed 16961

# Running tests:

F

Finished tests in 3.336265s, 0.2997 tests/s, 0.2997 assertions/s.

  1) Failure:
test_rename_column_with_multi_column_index(ActiveRecord::Migration::ColumnsTest) [test/cases/migration/columns_test.rb:99]:
--- expected
+++ actual
@@ -1 +1 @@
-["index_test_models_on_hat_style_and_size"]
+["i_test_models_hat_style_size"]


1 tests, 1 assertions, 1 failures, 0 errors, 0 skips
```

Since #8645 has been merged, Oracle enhanced adapter supports its feature in rsim/oracle-enhanced#286. But because of its maximum index length is 30 bytes, Oracle enhanced adapter shortens its name if it is longer than 30 byte.