FIP-87: PCV Sentinel

Summary/Specification:

The PCV Sentinel will be deployed and granted the role of “GUARDIAN” (the same role as the multisig guardian. The Tribe DAO authorizes the multisig guardian to add automated policies to the PCV Sentinel to protect the PCV, automate key protocol features such as the PSM, the collateralization oracle, and other system-critical components.

For additional details please see the forum post here: https://tribe.fei.money/t/fip-87-pcv-sentinel/4018

The code for the PCV Sentinel can be viewed here: https://github.com/fei-protocol/fei-protocol-core/pull/506

Voting:

The proposal will use simple-choice yes/no voting.