[SDK] Add utility class

[Utilitycoder]

A helper class to subscribe to balance changes for specific tokens/addresses involved in streams using RPC polling or event subscription.

[mandyslovestories-sudo]

@mandyslovestories-sudo has applied to work on this issue as part of the Stellar Wave Program's 4th wave.

I'd love to work on this issue

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[drips-wave]

Congratulations, @mandyslovestories-sudo! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on April 29, 2026.

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