simplify scheduling in distributeFees

[Chris-Hibbert]

What is the Problem Being Solved?

vats/src/distributeFees.js tries to throttle multiple deposits in too complex a way.

Description of the Design

@michaelfig said

if we still need the deposit-to-all functionality, we should rip out the batching/queuing/depositMultiple/delays and just fire off Promise.all(accounts.map(acct, i) => E(bank).deposit(acct, payment[i])), and let the scheduler decide how to handle many messages. It was premature optimisation, and in the wrong place (any changes to make this efficient should be made in the scheduler instead of per-vat).

Security Considerations

Should be performance only.

Test Plan

existing tests should be sufficient, since the code will get simpler and require fewer parameters.