Remove intermediate strings in json deserialization to reduce memory usage

[alecrodden]

Improvements made:

• Replaced multiple instances of HttpContent.ReadAsStringAsync() + JsonNode.Parse(string) with HttpContent.ReadAsStreamAsync() + JsonNode.ParseAsync(Stream).
• Replaced multiple instances of JsonSerializer.Deserialize<T>(responseNode.ToString()) with JsonSerializer.Deserialize<T>(responseNode).

[google-cla]

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[shivvaam0001]

Hi @alecrodden
Thank you for your contribution. Please check the failing checks and update the same.

Thanks!