tests: add unit tests for client recovery

[seanchen1991]

Description

Adds unit tests for validating client recovery functionality in ibc-testkit.

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PR author checklist:

• [ ] Added changelog entry, using unclog.
• [ ] Added tests.
• [ ] Linked to GitHub issue.
• [ ] Updated code comments and documentation (e.g., docs/).
• [ ] Tagged one reviewer who will be the one responsible for shepherding this PR.

Reviewer checklist:

• [ ] Reviewed Files changed in the GitHub PR explorer.
• [ ] Manually tested (in case integration/unit/mock tests are absent).

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 27.27273% with 8 lines in your changes are missing coverage. Please review.

Project coverage is 63.98%. Comparing base (083b6b4) to head (4b33ac9).

Files	Patch %	Lines
ibc-core/ics25-handler/src/entrypoint.rs	0.00%	8 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## sean/client-recovery #1151 +/- ## ======================================================== + Coverage 63.55% 63.98% +0.43% ======================================================== Files 219 219 Lines 21305 21313 +8 ======================================================== + Hits 13541 13638 +97 + Misses 7764 7675 -89 ```

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