Adopt shared mapper test data from engine-test-data

Mapper tests use inline expected context data. When engine-test-data releases shared mapper test cases, this client should adopt them for cross-SDK consistency.

## Acceptance criteria
- [ ] Mapper test uses expected context from engine-test-data
- [ ] mapper_test_cases pass (see Flagsmith/engine-test-data#46)

## Technical context

Test data: https://github.com/Flagsmith/engine-test-data/pull/46

从 mapper 测试开始，将其中 inline 的 expected context data 与 engine-test-data PR #46 中共享的 mapper cases 进行比较。当测试使用该共享的 expected context 且 mapper_test_cases 通过时，即完成。

由索引模型根据 Issue 内容生成。