Refactor chain- and epoch-specific state manager tests into a dedicated file #7723

Summary

Move chain- and epoch-specific tests out of src/state_manager/utils.rs into a dedicated test file or test module. This is a follow-up refactor to PR #7709. It does not change state manager or RPC behavior.

Rationale

src/state_manager/utils.rs contains state-computation helpers and tests for specific network epochs. A dedicated test file will separate these responsibilities and make the snapshot-based tests easier to find and maintain.

Required changes

• Move cargo_test_reward_distribution_calibnet_4109134 into a dedicated test file or test module.
• Move the related chain- and epoch-specific replay and state-validation tests from state_compute::tests into the dedicated test organization.
• Review the generated state-computation test inclusion and keep generated tests discoverable.
• Keep reusable snapshot download and state preparation helpers available to the moved tests.
• Preserve test names, assertions, Tokio runtime settings, and #[fickle::fickle] annotations.

Affected areas

• src/state_manager/utils.rs, particularly state_compute::tests.
• The new dedicated state manager test file or test module.
• Test module declarations and generated-test inclusion, as needed.

Acceptance criteria

• Chain- and epoch-specific tests no longer reside in src/state_manager/utils.rs.
• The moved tests remain discoverable and retain their existing coverage.
• Snapshot loading, state-root checks, reward accounting assertions, and cache assertions remain unchanged.
• Relevant tests pass under the existing test workflow.
• No production state manager or RPC behavior changes.

References

• PR: feat(api): state reward distribution v2 api #7709
• Review thread: feat(api): state reward distribution v2 api #7709 (comment)
• Requested by: @akaladarshi