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