[PVM] Adjustment of validator uptime on reactivation

[charalarg]

Description

This PR adjusts the uptime of a suspended validator at its reactivation time because by default when its moved back to the current set, its uptime starts from 0 but the uptime percentage is calculated from its initial start time ending up in an invalid value.

Important note: This invalid value is only stored on a mapping in state and not on disc. And this happens because when we reactivate the validator, the LoadUptime is being called which is not altering anything on disc. So, if we boot up a brand new node and request the uptime of the reactivated validator it will be calculated from its initial value.

With this PR we are updating the uptime of the reactivated validator both on the mapping and in db's state, thus they will be in sync.

Changes

• Added the setValidatorUptime call on validator reactivation
• implemented the setValidatorUptime function in state
• In order to call state's original setUptimefunction we needed to make a cross reference between state and caminoState.

Remarks

This implementation is just a POC proving that the uptime update works.
Further discussions, thoughts and tests needed in order to conclude to this implementation

[c4t-ag]

Wouldn't it be much easier regarding implementation if we wrap the *Staker around a struct which has a member "suspendedUptime"? Something like:

struct {
  Staker
  suspendUptime
}