enable Reserve (under governance) to sell asset via Auction

[Chris-Hibbert]

What is the Problem Being Solved?

The current design for VaultLiquidation (#7047) may result in collateral accumulating in the reserve.

Description of the Design

The Reserve should acquire the ability to send assets to the Auction for liquidation, at the behest of its governing contract.

Security Considerations

governance issues, and economic considerations.

Scaling Considerations

Scaling is not an issue. This would be occasional, committee-directed messages, resulting in more assets for the Auction to dispose of. The auction will already be running regularly.

Test Plan

Verify that governance can invoke the new functionality. Notice ##7072.