go/keymanager/churp: Require stake for every churp scheme

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🔨 Latest commit	516d61eb66a4d4c6887bec6f9976b466cac89659
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[codecov[bot]]

Codecov Report

Attention: Patch coverage is 63.82114% with 89 lines in your changes are missing coverage. Please review.

Project coverage is 65.27%. Comparing base (1eaa8c0) to head (0731ad1). Report is 4 commits behind head on master.

:exclamation: Current head 0731ad1 differs from pull request most recent head 516d61e. Consider uploading reports for the commit 516d61e to get more accurate results

Files	Patch %	Lines
go/staking/api/sanity_check.go	57.14%	24 Missing and 6 partials :warning:
...o/consensus/cometbft/apps/registry/transactions.go	30.76%	22 Missing and 5 partials :warning:
go/registry/api/sanity_check.go	70.37%	5 Missing and 3 partials :warning:
go/consensus/cometbft/apps/keymanager/churp/txs.go	81.81%	3 Missing and 3 partials :warning:
...sensus/cometbft/apps/supplementarysanity/checks.go	50.00%	3 Missing and 3 partials :warning:
go/upgrade/migrations/consensus_240.go	44.44%	2 Missing and 3 partials :warning:
go/keymanager/churp/sanity_check.go	81.81%	2 Missing and 2 partials :warning:
go/consensus/cometbft/apps/registry/registry.go	66.66%	0 Missing and 2 partials :warning:
go/oasis-node/cmd/stake/stake.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #5653 +/- ## ========================================== - Coverage 65.50% 65.27% -0.23% ========================================== Files 596 597 +1 Lines 61569 61681 +112 ========================================== - Hits 40328 40260 -68 - Misses 16520 16705 +185 + Partials 4721 4716 -5 ```

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