Drop Pending Stakers

[abi87]

Context and scope
See https://github.com/avalanche-foundation/ACPs/blob/main/ACPs/41-remove-pending-stakers.md

Open questions
How should we specify staking duration?
In previous iterations we chose to specify duration as EndTime-StartTime. So StartTime and EndTime are non meaningful by themselves , but their difference is the duration that is validated and accepted.
Current ACP chooses to specify EndTime, so that duration is EndTime - currentChainTime.

Structure
Review PRs from Drop Pending Stakers 0 to Drop Pending Stakers 5

[github-actions]

This issue has become stale because it has been open 60 days with no activity. Adding the lifecycle/frozen label will cause this issue to ignore lifecycle events.

[abi87]

Done with Durango fork