refactor: generalize `ibc-testkit` types to allow remote storage and light clients

[rnbguy]

Closes: #1269

Description

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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 97.14286% with 6 lines in your changes missing coverage. Please review.

Project coverage is 67.49%. Comparing base (7ff41b3) to head (9236182).

Files	Patch %	Lines
ibc-testkit/src/relayer/context.rs	86.20%	4 Missing :warning:
ibc-testkit/src/testapp/ibc/core/types.rs	71.42%	2 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #1270 +/- ## ========================================== + Coverage 67.42% 67.49% +0.06% ========================================== Files 235 235 Lines 23811 23883 +72 ========================================== + Hits 16055 16120 +65 - Misses 7756 7763 +7 ```

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