Oracle: provide mechanism to export custom image to object storage bucket

In order to test different deployment environments in Oracle, pycloudlib needs the ability to export custom images to a custom Oracle object storage bucket.

This may entail the following features:
- [ ] [enumerate any existing Oracle object storage buckets](https://docs.oracle.com/en-us/iaas/tools/python/2.91.0/api/object_storage/client/oci.object_storage.ObjectStorageClient.html#oci.object_storage.ObjectStorageClient.list_buckets)
- [ ] [Create new object storage bucket if not present](https://docs.oracle.com/en-us/iaas/tools/python/2.91.0/api/object_storage/client/oci.object_storage.ObjectStorageClient.html#oci.object_storage.ObjectStorageClient.create_bucket)
- [ ] [compute_client.create_image to export to an Oracle Object storage bucket](https://docs.oracle.com/en-us/iaas/tools/python/2.91.0/api/core/client/oci.core.ComputeClient.html?highlight=custom%20image#oci.core.ComputeClient.create_image)