Staking event updates/improvements

[ptrus]

AddEscrowEvent: include amount of shares that the were obtained in the event
ReclaimEscrowEvent: include amount of shares that were reclaimed in the event

Currently on escrow, one cannot know the amount of shares the escrow resulted in without querying the staking state (before and after the operation), or by manually calculating the share price at the exact height of the escrow. Adding the amount of shares to the AddEscrowEvent solves this.

Similarly for ReclaimEscrowEvent to know the amount of shares that were reclaimed one would need to query DebondingDelegations before the emitted event and match the reclaimed amount/epoch with the delegation.

In both cases we have the amount of share information available when we emit these events, it is just not included in the events.

Note: changing events is a breaking (but currently not a consensus-breaking) change.