Test RoT and bootloader updates with reconfigurator CLI

[karencfv]

In order to reliably be able to test RoT and RoT bootloader updates with the reconfigurator-cli, we'll need fake artifacts that contain a caboose. Specifically, because the planner does a check against the sign within the caboose of each RoT/RoT bootloader artifact.

We have https://github.com/oxidecomputer/hubtools/blob/main/hubtools/src/archive_builder.rs#L33-L77 which probably needs to be updated to add a SIGN. Most likely we could extend tufaceous to add this.

Related: #8421 (review)

[karencfv]

Closed by #8835