Pending DualGovernance state

[Psirex]

• Rename method getState() to getPersistedState().
• Introduce method getEffectiveState(), which returns the state that DualGovernance would transition to upon calling the DualGovernance.activateNextState() method.
• Include information about both persisted and effective states in the StateDetails struct.
• Introduce a new getter DualGovernance.canCancelAllPendingProposals().
• Use effective state in the following getters: canSubmitProposal(), canScheduleProposal(), getTiebreakerDetails(), canCancelAllPendingProposals().
• Move the configProvider field into the DualGovernanceStateMachine.Context struct.
• Call activateNextState() as the first action in the DualGovernance.resealSealable() method.
• Call activateNextState() as the first and last action in the Escrow.markUnstETHFinalized() method.
• Call DualGovernance.activateNextState() as the first action in the Escrow.requestWithdrawals() method.
• Update the specification with the newly introduced changes.
• Fix any failed tests.
• Add tests for all newly introduced methods.
• Return bool flag from the cancelAllPendingProposals() method.
• Add NatSpec comments to DualGovernance, Escrow contracts, and DualGovernanceStateMachine, DualGovernanceStateTransitions libs.

[bulbozaur]

LGTM

[sandstone-ag]

LGTM