Feature: Add the ability to detect how fast validators restart if the network goes down

[buffalu]

Is your feature request related to a problem? Please describe.
In the rare scenario that the Solana network goes down, the speed that validators start up is extremely important for resuming operations. StakeNet should be able to measure how fast validators come back online and track this data, penalizing validators that are slow to respond.

Describe the solution you'd like
StakeNet can track how fast a validator gets back online and keep track of it.

Describe alternatives you've considered
N/A

Additional context
N/A

[ebatsell]

The LastRestartSlot may be useful here