Test more Python evaluation results

[HenryRLee]

Currently, in Python, the unit tests for our 5-card, 6-card, and 7-card evaluator are using data set in 5cards.json, 6cards.json, and 7cards.json. The dataset is small and fixed. So the test coverage is far from enough.

Since we cannot use Kev's evaluator like the C++ code, my idea would be something like this:

1. For 5-card evaluation, generate all possible hands and stored them in 5cards.json. There will be 2,598,960 lines, which is acceptable. (I just found that we happened to have this data set under ../tree/develop/test/five).
2. For 6-card and 7-card evaluation, randomly sample thousands of hands, and brute force the expected result using the 5-card evaluator. This is similar to the unit test case used in the Omaha test.