async flow membrane doesn't preserve Brand identity

[dckc]

Describe the bug

When a host function returns a Brand, the guest sees a Brand guest wrapper that isn't useful for brand identity comparison.
Issuers likewise, presumably.

To Reproduce

1. Check out the dc-brand-info branch - currently 8c772e6
2. cd agoric-sdk/packages/orchestration
3. yarn test test/facade.test.ts -m 'asset / denom info'
4. test fails due to difference between brand and brand guest wrapper and

 asset / denom info
  test/facade.test.ts:196

  -   brand: Object @Alleged: Token1 brand guest wrapper { ...  },
  +   brand: Object @Alleged: Token1 brand {},

  1 test failed

Expected behavior

Brand returned in orch.getBrandInfo() can be compared by identity as usual.

Additional context

#9754, #9211

[mhofman]

This is "working as intended". The test above attempts to compare a value inside the orchestrated function with a value captured in the context outside of it.

[dckc]

So the problem here was flows that closed over the brand. Following the norms for flows (#9692, #9693) means passing the brand in as an endowment, at which point the identity comparison works.