bootstrap upgrade complicated by 5 non-durable exports

[dckc]

Describe the bug

The bootstrap vat has 5 non-durable objects. So upgrading it will sever those exports; in particular, the coreEval handler, provisioningHandler, and prioritySenders manager.

To Reproduce

agoric-sdk/packages/boot/test/bootstrapTests/test-vaults-upgrade.ts

Lines 158 to 170 in 7386420

	test.serial('audit bootstrap exports', async t => {
	const expected = {
	maxExports: 5,
	maxNonDurable: 5,
	ifaces: {
	// in bridgeCoreEval()
	coreHandler: true,
	// in bridgeProvisioner()
	provisioningHandler: true,
	'prioritySenders manager': true,
	// TODO? move to provisioning vat?
	clientCreator: true,
	},

Expected behavior

A clear and concise description of what you expected to happen.

Platform Environment

all platforms since mainnet1B launch.

Additional context

This issue is mainly to provide back-pointers to work that it impacts.

[Chris-Hibbert]

The provisioningHandler here may actually be the one from chainBehaviors. There are two objects defined as Far('provisioningHandler', ...). One in chainBehavior, and another in provisionPoolKit. The latter is expected to be replaced with an Exo (see #10419), possibly as soon as upgrade 19.