WIP: full measurements in reconfigurator

[labbott]

This is the full stack of changes to support reference measurements. This is described more fully in RFD 512 but briefly: the goal here is to be able to distribute a set of reference measurements (hashes of what software we expect to be running on the rack) to sprockets so sprockets can appraise the measurements (compare what's actually running on the rack to the expected reference measurements).

Blueprints now have knowledge of measurements (see omicron#9718) and this PR stack is responsible for having reconfigurator update the measurements. Measurements are an artifact in the TUF repo. The high level goals here are

• Handle going from a blueprint with Unknown measurements (the default when pulling out old blueprints) to a known set of measurements
• Support reading measurements from the install dataset during a MUPdate override situation
• Making sure the measurements included on each sled include all the measurements from the old TUF repo and the new TUF repo. This is the only set of software we ever expect to be running.
• Updating the measurements before performing any other changes to the sled

Big points to check

• MUPdate override must always work as this will be the recovery path. This will be even more important when measurements are enforced (right now it's logged but the sprockets connection continues)
• Is this right place for measurements to come first in reconfigurator? Right now we're only measuring RoT and SP but Host OS is coming soon. Will we need changes when that happens?
• Are there enough test cases with the reconfigurator-cli?
• The edit counts for measurements with the sled-editor never felt quite right. Is there a better way to check?