make vat-network upgradable

[warner]

What is the Problem Being Solved?

As part of #5666 we need to make the "network vat" upgradable. This vat hosts a copy of
SwingSet/src/vats/network/router.js.

I'm not sure what this will entail (I'm not very familiar with this network code).

Description of the Design

This includes not only making the network vat durable, but also providing a utility for clients of the network vat (such as Pegasus or ICA) to tolerate an upgrade (and its broken promises) without losing precious state.

Security Considerations

Test Plan

Tasks

Beta Give feedback

1. Implement Vows for upgrade-tolerant promise behaviour #8906
   enhancement +1
   
2. feat!: make Network and IBC vats durable #8721
   automerge:squash +1
3. add interface guards to network, ibc vats #8950
   enhancement +1
   
4. test: upgrading ibc/network vats at many points in protocol #8948
   +0
5. Convert awaits in network and ibc vats to promise watcher #8867
   2 of 2
   enhancement needs-design +2
   

[warner]

@gibson042 could you take a look at this and see how feasible it seems?

[warner]

@FUDCo walked through the packages/SwingSet/src/vats/network/ code today.. we're thinking that maybe it should be moved out of swingset, either into packages/vats/ that uses it, or into its own package.

His preliminary assessment is that making it upgradable wouldn't be too hard.

[Tartuffo]

@FUDCo making you the primary on this.

[FUDCo]

I spoke with @michaelfig and he said that moving this to packages/vats was reasonable, since it isn't really managed like the other vats that are part of SwingSet but is more of an IBC thing. Apparently the primary reason this got put into packages/SwingSet was that packages/vats didn't exist at the time.

[warner]

break this into two pieces:

• reachably durable (Upgradable network vat #5973)
• known (tested) to be upgradable

We can defer the upgrade testing for after the pso milestone.

[dckc]

vat-network wasn't in the pismo vats. I think it's only needed for dyanimc IBC, which isn't a vaults release feature

cc @warner @michaelfig