Reorganize testing modules

[kaimen-sano]

Description and Motivation

Moves the Osmosis mocking to the white-whale-testing package, rather than white-whale-std package. This lets us drop the #[cfg(test)] qualifiers which restrict integration tests from consuming our package.

This is a suitable restriction to drop, since it is likely that any code that is using white-whale-testing is performing testing operations, while our white-whale-std was public facing.

Fixing such issue is necessary, as we currently cannot cargo test on the release/v2_contracts branch.

Related Issues

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Checklist:

• [X] I have read Migaloo's contribution guidelines.
• [X] My pull request has a sound title and description (not something vague like Update index.md)
• [X] All existing and new tests are passing.
• [X] I updated/added relevant documentation.
• [X] The code is formatted properly cargo fmt --all --.
• [X] Clippy doesn't report any issues cargo clippy -- -D warnings.
• [X] I have regenerated the schemas if needed cargo schema.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 88.20%. Comparing base (eabfd9b) to head (d1a8b19). Report is 3 commits behind head on release/v2_contracts.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## release/v2_contracts #296 +/- ## ===================================================== Coverage 88.20% 88.20% ===================================================== Files 250 250 Lines 23424 23424 ===================================================== Hits 20660 20660 Misses 2764 2764 ```

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