Add more popular datasets to graphscope built-in datasets

We have several built-in datasets that can be easily loaded in one-line, located in the `dataset` directory of Aliyun OSS bucket `graphscope`, and the corresponding utility function to load them, located in `python/graphscope/dataset/`. We are planning to enrich the datasets continuously.

There's the procedure to add new datasets:
1. Find a popular and appropriate dataset, adapt the format to property graph if necessary,
2. Put all data files inside a folder, give the folder a meaningful name,
3. Compress the folder, then upload the compressed file **together with the original folder** to the `dataset` folder of the OSS bucket. Assume you have a folder named `foo/`, and two files `foo/nodes.csv` and `foo/edge.csv`, after this step, you will have the following file structure in the bucket:
```
dataset
|-- foo.tar.gz
|-- foo
|-- nodes.csv
|-- edge.csv
```
4. Write the loading function `load_foo` in a new file named `python/graphscope/dataset/foo.py`.
5. A corresponding unit test is appreciated!