Add embed endpoint

[rohanshah18]

Problem

Add embed endpoint for Java SDK to allow users to create embeddings for text data such as passage or query using a specified model. More details on inference api can be found here.

Solution

Users can now call embed endpoint with the following parameters:

1. String model: Accepts a string from the specified models .
2. Map<String, Object> parameters: Accepts input_type and truncate as keys with their corresponding values in a Map. The values are expected to be scalar. Please note that the default value of truncate is set to END if not specified.
3. List<String> inputs: The list must be of size atleast 1.

As a part of this change, I have added a getInferenceClient() in Pinecone class to follow a similar pattern with other SDKs. The underlying client uses OkHTTPClient for REST calls. The method getInferenceClient() returns an instance of Inference class which I added as a wrapper to the Inference API. So far, this wrapper contains embed() endpoint only, with the plan of adding rerank() soon. Lastly, I have added docstrings and updated README with an example of the embed endpoint.

Type of Change

• New feature (non-breaking change which adds functionality)

Test Plan

Added integration tests.

[aulorbe]

Just some language nits :)

[austin-denoble]

Overall looks good to me, I agree with the feedback @ssmith-pc left as well.

[austin-denoble]

LGTM, thanks for iterating.

[ssmith-pc]

I left a couple more comments related to code samples, but overall looks good to me. Thanks for addressing all the feedback.