Deprecate and remove findStateAtEvent method in StateService

[coderabbitai]

Description

The findStateAtEvent method in StateService is marked with a TODO comment indicating it should be removed.

Location: packages/federation-sdk/src/services/state.service.ts (around line 897)

Current State

The method is marked with // TODO: remove this and currently wraps getStateAtEvent.

Suggested Migration Path

1. Add a JSDoc @deprecated annotation to the method pointing users to getStateAtEvent
2. Identify and migrate all callers to use getStateAtEvent directly
3. Remove commented-out tests in state.service.spec.ts that reference this TODO
4. Remove the method once all migrations are complete

Context

• PR: refactor: state calculation #252
• Comment: refactor: state calculation #252 (comment)
• Requested by: @debdutdeb