Add CoordsSchema support to DatasetSchema

[calgray]

This change largely adds support for passing coordinates to DatasetSchema. This additionally involves:

• Extending test_component_raises_schema_error to support multiple schema arguments and add more test cases. This allows testing CoordsSchema and AttrsSchema with allow_extra_keys and require_all_keys.
• Updated _json_schema for dataset, coords, and attrs to be explicit about required and additional properties based on constructor signatures. This allows restoring the JSON schema assertions in tests.
• Adjusted AttrsSchema validation message and added test case.

Also, thank you for this great pandera-like library 💯

[calgray]

Related to #187