Clean up `ibc-core` and `ibc-clients` error types

[seanchen1991]

Part of: #1316

Description

---

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 58.81188% with 208 lines in your changes missing coverage. Please review.

Please upload report for BASE (error-handling@0d98ebf). Learn more about missing BASE report.

Files	Patch %	Lines
ibc-core/ics25-handler/types/src/msgs.rs	0.00%	19 Missing :warning:
ibc-core/ics23-commitment/types/src/merkle.rs	5.26%	18 Missing :warning:
ibc-clients/ics07-tendermint/types/src/header.rs	60.00%	14 Missing :warning:
ibc-testkit/src/testapp/ibc/core/core_ctx.rs	62.06%	11 Missing :warning:
ibc-core/ics02-client/types/src/events.rs	74.35%	10 Missing :warning:
...ore/ics24-host/cosmos/src/upgrade_proposal/plan.rs	0.00%	9 Missing :warning:
...core/ics24-host/cosmos/src/validate_self_client.rs	0.00%	9 Missing :warning:
ibc-core/ics04-channel/src/handler/timeout.rs	27.27%	8 Missing :warning:
...core/ics04-channel/src/handler/timeout_on_close.rs	46.66%	8 Missing :warning:
...clients/ics07-tendermint/types/src/misbehaviour.rs	41.66%	7 Missing :warning:
... and 37 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## error-handling #1317 +/- ## ================================================= Coverage ? 67.18% ================================================= Files ? 227 Lines ? 23264 Branches ? 0 ================================================= Hits ? 15631 Misses ? 7633 Partials ? 0 ```

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