feat: proposer and sequencer set decoupling

[keruch]

PR Standards

Opening a pull request should be able to meet the following requirements

ADR link: https://www.notion.so/dymension/Sequencer-Rotation-Internal-audit-124a4a51f86a8066abf5ec64463cf391#125a4a51f86a80c9833cf3ee3a7b8391

ADR checklist:

• [x] Track the non-active sequencer set (in the state but not in the store)
• [X] Sequencer set is moved from the state to the manager
• [X] Sequencer set is deleted from the store
• [x] Sequencer set contains all sequencers the rollapp ever had (bonded + unbonded)
• [x] State keeps the proposer separately
• [x] Save proposer by height in the store / Get proposer by height from the store
• [x] Proposer might be nullable (in both state and store)
• [x] Only return the proposer as a valset in RPC queries -> Dan did it lately https://github.com/dymensionxyz/dymint/pull/1159
• [x] State Is not used in Execute Block
• [ ] Query lazily the entire set before rotation -> next PR
• [ ] Bonded Sequencer event is Redundant -> next PR

Close

1149

https://github.com/dymensionxyz/dymint/issues/1152

For Author:

• [x] Targeted PR against correct branch
• [x] included the correct type prefix in the PR title
• [x] Linked to Github issue with discussion and accepted design
• [x] Targets only one github issue
• [x] Wrote unit and integration tests
• [x] All CI checks have passed
• [x] Added relevant godoc comments

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For Reviewer:

• [ ] confirmed the correct type prefix in the PR title
• [ ] Reviewers assigned
• [ ] confirmed all author checklist items have been addressed

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After reviewer approval:

• [ ] In case targets main branch, PR should be squashed and merged.
• [ ] In case PR targets a release branch, PR should be rebased.