refactor: improve subspaces keeper input/output consistency

[dadamu]

Description

This PR improves subspace keeper input and output consistency.

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Author Checklist

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I have...

• [x] included the correct type prefix in the PR title
• [ ] added ! to the type prefix if API or client breaking change
• [x] targeted the correct branch (see PR Targeting)
• [ ] provided a link to the relevant issue or specification
• [ ] followed the guidelines for building modules
• [ ] included the necessary unit and integration tests
• [ ] added a changelog entry to CHANGELOG.md
• [ ] included comments for documenting Go code
• [ ] updated the relevant documentation or specification
• [x] reviewed "Files changed" and left comments if necessary
• [ ] confirmed all CI checks have passed

Reviewers Checklist

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I have...

• [ ] confirmed the correct type prefix in the PR title
• [ ] confirmed ! in the type prefix if API or client breaking change
• [ ] confirmed all author checklist items have been addressed
• [ ] reviewed state machine logic
• [ ] reviewed API design and naming
• [ ] reviewed documentation is accurate
• [ ] reviewed tests and test coverage
• [ ] manually tested (if applicable)

[codecov[bot]]

Codecov Report

Patch coverage is 59.09% of modified lines.

Files Changed	Coverage
app/app_config.go	ø
app/wasm_config.go	ø
x/subspaces/module.go	0.00%
x/subspaces/keeper/invariants.go	87.50%
app/app.go	100.00%
x/subspaces/abci.go	100.00%
x/subspaces/keeper/keeper.go	100.00%
x/subspaces/keeper/msg_server.go	100.00%
x/subspaces/wasm/querier.go	100.00%

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