Test succinct delegations

[jku]

This is not on any critical path (as I don't know of repositories using succinct delegations) but:

We should add a basic test for succinct delegations at some point:

• I don't remember how the spec defines this but I would consider this an optional feature of the spec so should make this easy to make "expected to fail"
• there is some functionality in RepositorySimulator to create these things already

[jku]

I don't remember how the spec defines this but I would consider this an optional feature of the spec so should make this easy to make "expected to fail"

Turns out this is still an augmentation proposal: we'll have to figure out how we handle optional features.
My first instinct is just action inputs like

tap15-succinct-hashed-bin-delegations:
   default: "false"

and some way to do that with the command line as well

[jku]

I wanted to close the PR since it's unlikely to move forward before we have a solution for the "optional features" but I also wanted to preserve the work: it's now in succint-graph-traversal branch.

[jku]

it's unlikely to move forward before we have a solution for the "optional features"

It looks like there's not a lot of demand for "optional features" flags so I guess we can handle this one with just the existing "xfails" approach: clients that don't support succinct delegations can just mark the test as expected to fail.

So the existing branch could be rescued:

• it will need fixes because infra code has changed a bit
• there are comments in add test for succint role test case #141 that would need to be addressed