Replaced the anonymous request shapes of the providers with records

app/Tests/Serialization/Fixtures/embedding-request.json

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+{"model":"embedding-model","input":["The first text.","The second text."],"encoding_format":"float"}

app/Tests/Serialization/Fixtures/google-embedding-request.json

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+{"content":{"parts":[{"text":"The first text."},{"text":"The second text."}]},"task_type":"SEMANTIC_SIMILARITY"}