Don't hit the real PokeAPI with the tests

[sargunv]

• Use a local instance of PokeAPI to generate a copy of every JSON, and put it in src/test/resources
• Make the current tests call a mock client that actually hits the local files instead of the live PokeAPI
• Enable the BulkTest which is disabled now because it's a heavy test
• Add one or two basic tests that still hit the real PokeAPI.

This will greatly speed up the tests. However, we should be sure to regenerate the local copy of the data periodically to ensure the tests remain relevant. Maybe automate this by setting up a server that pulls everything from PokeAPI once a week or so and creates a PR here automatically?

[sargunv]

Didn't enable BulkTest since it's still pretty slow (but not nearly as slow as before)