Modified generator to generate plugins

[saimedhi]

Description

Modified the generator to generate plugins. Currently, it generates KNN APIs. I will add integration tests.

• Generated unit tests for all generated APIs is still pending and need to be done.

Issues Resolved

Closes #693 Closes #697

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 72.14%. Comparing base (b2a1796) to head (39273af). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #700 +/- ## ======================================= Coverage 72.14% 72.14% ======================================= Files 89 89 Lines 7945 7945 ======================================= Hits 5732 5732 Misses 2213 2213 ```

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[saimedhi]

Lint is failing. I will fix it in spec.

************* Module opensearchpy._async.plugins.knn
opensearchpy/_async/plugins/knn.py:232:8: C0103: Argument name "nodeId" doesn't conform to snake_case naming style (invalid-name)
************* Module opensearchpy.plugins.knn
opensearchpy/plugins/knn.py:[23](https://github.com/opensearch-project/opensearch-py/actions/runs/8364328461/job/22899396250?pr=700#step:5:24)2:8: C0103: Argument name "nodeId" doesn't conform to snake_case naming style (invalid-name)

[saimedhi]

READY FOR REVIEW.

• I'll include the generated KNN plugin and integration tests in the upcoming PR.

Currently facing issues with testing train_model, which are unrelated to the client. Followed documentation while writing tests.

knn train_model response {'model_id': 'my-model'}

knn get_model response {'model_id': 'my-model', 'model_blob': '', 'state': 'failed', 
'timestamp': '2024-03-22T06:44:52.102263Z', 'description': 'My model description', 
'error': 'Failed to execute training. May be caused by an invalid method definition 
or not enough memory to perform training.', 'space_type': 'l2', 'dimension': 4, 'engine': 'faiss'}

• All KNN plugin generated APIs are functional and callable.