chore: Fix slash veto demo flake

[spalladino]

The slash_veto_demo e2e test was failing since a view-like call to the contract to get the committees slashed for a given round reverted:

21:15:59   ● veto slash › vetoes true and sets the new tally slasher
21:15:59 
21:15:59     ContractFunctionExecutionError: The contract function "getSlashTargetCommittees" reverted.
21:15:59 
21:15:59     Error: ValidatorSelection__InsufficientValidatorSetSize(uint256 actual, uint256 expected)
21:15:59                                                            (0, 4)
21:15:59      
21:15:59     Contract Call:
21:15:59       address:   0x9debab8762554f8b8f5dfad92e40c1c7d2b0263a
21:15:59       function:  getSlashTargetCommittees(uint256 _round)
21:15:59       args:                              (3)
21:15:59       sender:    0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266
21:15:59 
21:15:59     Docs: https://viem.sh/docs/contract/simulateContract
21:15:59     Version: viem@2.23.7
21:15:59 
21:15:59       71 |     }
21:15:59       72 |     /** Returns the slash actions and payload address for a given round (zero if no slash actions) */ async getPayload(round) {
21:15:59     > 73 |         const { result: committees } = await this.contract.simulate.getSlashTargetCommittees([
21:15:59          |                                        ^
21:15:59       74 |             round
21:15:59       75 |         ]);
21:15:59       76 |         const tally = await this.contract.read.getTally([
21:15:59 
21:15:59       at getContractError (../../node_modules/viem/utils/errors/getContractError.ts:78:10)
21:15:59       at simulateContract (../../node_modules/viem/actions/public/simulateContract.ts:308:11)
21:15:59       at TallySlashingProposerContract.getPayload (../../ethereum/dest/contracts/tally_slashing_proposer.js:73:40)
21:15:59       at e2e_p2p/slash_veto_demo.test.ts:247:40
21:15:59       at retryUntil (../../foundation/dest/retry/index.js:84:24)
21:15:59       at e2e_p2p/slash_veto_demo.test.ts:310:32
21:15:59 
21:15:59     Cause:
21:15:59     ContractFunctionRevertedError: The contract function "getSlashTargetCommittees" reverted.
21:15:59 
21:15:59     Error: ValidatorSelection__InsufficientValidatorSetSize(uint256 actual, uint256 expected)
21:15:59                                                            (0, 4)

My guess is this happened because the round queried included early epochs where the committee had not yet been formed, so one of the calls to the rollup to get the committee failed, causing the entire call to fail even if other epochs in the round did have committees.

This PR fixes the L1 contract so it try/catches calls to the rollup and returns whatever committees could be fetched.

[LHerskind]

💀