IPC: Checkpoint handling in the parent subnet

[adlrocha]

The design has been moved to the following doc

Tasks

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1. Define bottom-up checkpoint message type ipc-monorepo#315
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2. Implement CheckInterpreter for Ipc::BottomUpResolve ipc-monorepo#314
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3. Implement ExecInterpreter for Ipc::BottomUpResolve ipc-monorepo#313
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4. Implement checkpoint validation in the Gateway actor ipc-monorepo#312
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5. https://github.com/consensus-shipyard/fendermint/issues/193
6. List unexecuted checkpoints by the Gateway actor #310
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7. Propose resolved bottom-up checkpoints in ProposalInterpreter::prepare ipc-monorepo#309
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8. Check data availability of checkpoints in ProposalInterpreter::process ipc-monorepo#308
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9. Implement ExecInterpreter for Ipc::BottomUpExec #307
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10. Garbage collect executed checkpoints #227
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11. Resume CID resolution after restart #280
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12. Solidity method to execute checkpoint full-fat ipc-monorepo#278
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13. Solidity method to execute checkpoint low-fat #277
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14. Adjust circulating supply during top-down message execution ipc-monorepo#270
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