Revisit tvl subtraction upon unexepected spent of staking output

[gitferry]

The current implementation considers three events that could affect tvl of the system (staking, unbonding, staking expiry). However, this does not include all the events that could subtract the locked value, e.g. slashing and unexpected withdrawal. We should revisit this issue later and make sure confirmed/unconfired tvl calculation as well as the calculation in the api side aligned.

ref