Remove usage of gson

[Luna712]

Details

Sometime in the near future, cloudstream will be removing the gson dependency. Usage of gson was never officially supported, and it was just an implicit dependency of another dependency and thus accidentally included. This dependency will be removed in the near future, and usage of gson should be migrated to Jackson via methods from AppUtils instead. Thank you!

Found usages: https://github.com/search?q=repo%3ATeKuma25%2FIndoStream%20gson&type=code

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