Add emergency shutdown and governance proposal

[LHerskind]

Add noEmergency modifier to user initiated functions that will perform a non-reverting noop in case of emergency. The cooldown admin will control the switch.

• Add setEmergencyShutdown() only callable by cooldown admin
• Add getEmergencyShutdown() for easy access
• Add noEmergency modifier to:
  • stake
  • cooldown
  • stakeWithPermit
  • redeem
  • redeemOnBehalf
  • claimRewards
  • claimRewardsOnBehalf
  • claimRewardsAndStake
  • claimRewardsAndStakeOnBehalf
  • claimRewardsAndRedeem
  • claimRewardsAndRedeemOnbehalf