fix: implement resource hydration using Jasminb ResourceConverter

[jwilkinson87]

This pull request refactors and improves the resource hydration logic in the FormSubmissionVersion class, moving from a custom mapping approach to using Jasminb's ResourceConverter for JSON:API resource handling. It also removes legacy envelope/data classes, simplifies resource lookup, and updates related tests and models.

Refactor and improvement of resource hydration:

• Replaces custom resource mapping logic with Jasminb's ResourceConverter, enabling more robust and extensible JSON:API resource hydration in FormSubmissionVersion. This includes new helper methods for converter configuration and raw resource lookup.
• Removes legacy JsonApiEnvelope and JsonApiResourceData classes, as hydration now relies on Jasminb's converter and registered types.

API and test updates:

• Updates the public hydration API: introduces hydrateResourceById(id, clazz) as the primary method, and updates tests to use this new method instead of the old autoHydrateByIdAs. [1] [2]
• Improves type registry access with a synchronized method to retrieve all registered classes for converter configuration.

Minor improvements:

• Adds explicit @JsonProperty("id") annotation to the id field in the Image model for consistency.
• Minor test renaming for clarity.

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