Remove getBootstrapPayment() from Treasury

[Chris-Hibbert]

What is the Problem Being Solved?

The Treasury has a method getBootstrapPayment() designed to provide RUN for the vbank at startup. It won't be needed once we have access to pre-existing RUN at chain startup.

Description of the Design

Remove the method and anything that refers to bootstrapPayment. There's a test, and code in install-on-chain and vats/src/bootstrap.js.

Security Considerations

It will be hard to convince reviewers and ourselves that there is nothing else using this functionality.

Test Plan

Not needed once the code is gone.

[Tartuffo]

@Chris-Hibbert After various meetings, this ended up with a MN-1 tag AND in the Product Backlog pipeline (not MN-1 Backlog). Please modify appropriately for what it should actually be.

[dckc]

This came up while working on #4165 ; the plan @michaelfig and I came up with is: make a single-purpose centralSupply contract that just mints the initial central supply based on supplyCoins from genesis and deposits it using the bankManager.

initial draft: 4c55bca, bb83419