Investigate group invariants violation in CI tests

[amaury1093]

Summary of Bug

CI test-sim-nondeterminism showed a group policies: unique constraint violation invariant broken.

Version

• PR: refactor: Revert middlewares to antehandlers (part 1/2: baseapp) #11979
• CI run: https://github.com/cosmos/cosmos-sdk/runs/6476126161?check_suite_focus=true#logs=

Steps to Reproduce

It's non deterministic, might only happen on some seeds. It would be good to investigate if:

• using the same seed, if this broken invariant is also present on master
• if not present on master, if it's introduced by refactor: Revert middlewares to antehandlers (part 1/2: baseapp) #11979

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For Admin Use

• Not duplicate issue
• Appropriate labels applied
• Appropriate contributors tagged
• Contributor assigned/self-assigned

[julienrbrt]

Closing this, as the discussion is happening in #14833 and #15741.
Linked this PR in the above.