A timed account is an account, which releases its balance to be spent
gradually. The process of releasing frozen funds is defined as follows.
Until the cliff_time global slot is reached, the initial_minimum_balance
of mina is frozen and cannot be spent. At the cliff slot, cliff_amount
is released and initial_minimum_balance is effectively lowered by that
amount. Next, every vesting_period number of slots, vesting_increment
is released, further decreasing the current minimum balance. At some
point minimum balance drops to 0, and after that the account behaves
like an untimed one. *)