Do not convert json schema types to python types for tools in GenericProvider.

[qiuosier]

This PR fixes #16 .

The OCI GenAI APIs for models using the GenericProvider requires tools to use json schema types.
The tool parameter types prepared by LangChain are already json schema types. They should not be converted to python types.

[YouNeedCryDear]

@qiuosier
Can you update the test cases as well?

[qiuosier]

Hi @YouNeedCryDear , there seems to be errors on the existing tests, so I updated them. Some of the payloads are updated based on what I received from the API calls.
Also, I updated the PR with the following:

1. Fixed a bug in the _get_provider() function introduced by Support OpenAI and xAI models #13 , I made a mistake when updating the code.
2. Added a test(test_get_provider) for the _get_provider() function.
3. Added assertions to the mocked_response of test_meta_tool_conversion for checking the parameter types (updated by this PR).

Following is a screenshot of the test run outputs.