Increase primary network uptime requirement (ACP-267)

[michaelkaplan13]

Context and scope
Implement https://github.com/avalanche-foundation/ACPs/blob/main/ACPs/267-uptime-requirement-increase/README.md

Discussion and alternatives
After discussion, it was decided that it is best to enforce the higher uptime requirement only on a go-forwards basis. Validators that started before the ACP was created or announcement sent out should still only be required to meet the existing uptime requirement.

Changes to the uptime requirement do not require network upgrades because uptimes are locally observed by each node anyways. Each node votes on whether or not it prefers to reward a given validator by setting its initial preference based on its own observed uptime of that validator. The network-wide decision whether or not a reward is given to the validator is then reached through consensus.

[michaelkaplan13]

The functionality to be added for this issue is documented here.

There are 4 PRs to complete this issue. The first two are strictly refactoring to prepare for and reduce the diff of the primary implementation PR.

• refactor: staking config verification #4985
• refactor: platform vm tests initialization #4986
• feat: uptime requirement updates configuration #4987
  • Heart of the implementation.
  • (+495/-60) ~350 of the new lines are testing, and another ~40 documentation
• feat: ACP-267 90% uptime requirement activation #4988
  • Set specific uptime requirement and time that it becomes effective.