RandomBeacon.sol: surround staking.seize with try/catch

[nkuba]

I believe we should surround all calls to staking.seize function with a try/catch block, similar as we do with staking.slash.

If we don't do that challangeDkgResult may not be effective in case of any problems in the staking contract.

keep-core/solidity/random-beacon/contracts/RandomBeacon.sol

Lines 643 to 648 in c9e57b2

	staking.seize(
	slashingAmount,
	dkgMaliciousResultNotificationRewardMultiplier,
	msg.sender,
	operatorWrapper
	);

[nkuba]

Implemented for ECDSA Wallets: f03de3b