stop deep imports of agoric CLI package

[turadg]

Agoric/agoric-sdk#7824 attempted to remove exports from the agoric package so that it's only used for its bin install.

That broke loadgen CI,

(Error#1)
Error#1: Package subpath './lib/helpers.js' is not defined by "exports" in /usr/src/testnet-load-generator/runner/node_modules/agoric/package.json

  at resolve (file:///usr/src/testnet-load-generator/runner/lib/helpers/module.js:26:32)
  at getSDKBinaries (file:///usr/src/testnet-load-generator/runner/lib/main.js:172:33)
  at async Promise.all (index 0)
  at async main (file:///usr/src/testnet-load-generator/runner/lib/main.js:329:49)

For now I've restored the two exports loadgen expects,

testnet-load-generator/runner/lib/main.js

Lines 165 to 167 in 0e2b891

	const srcHelpers = 'agoric/src/helpers.js';
	const libHelpers = 'agoric/lib/helpers.js';
	try {

A more maintainable solution would be for the interface between loadgen and the agoric package to use the CLI.

[mhofman]

That one is gonna be tricky. If we rely on the CLI, we should add a CLI command to get the path of the binaries.

cc @michaelfig, any thoughts? I know you've been thinking about build artifacts, and this is somewhat relevant.