fix secrets inference endpoints (#2490)
* feat: :sparkles: allow passing secrets through the inference endpoint client
added the secrets argument to create_inference_endpoint, update_inference_endpoint and InferenceEndpoint.update
* test: :white_check_mark: add secrets to test
* Apply suggestions from code review
* fix: :bug: fix: allow not passing secrets at creation
* fix: :bug: remove default secret
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Co-authored-by: Lucain <lucainp@gmail.com>
