[24/n] [reconfigurator-planning] support no-op image source updates

[sunshowers]

RFD 556 discusses part of the mupdate recovery process being a zone image source switch from the install dataset to the TUF repo depot.

During discussions, we figured out that this doesn't have to be tied to the mupdate override stuff for the most part, and that this is a process we are allowed to perform on any zones where a mupdate override isn't in place.

This depends on some pending work in Sled Agent to treat image source switches as no-ops if the underlying hash is the same.

Depends on:

• [20/n] [reconfigurator-planning] do decommission before add #8464
• sled-agent should not bounce zones if the image source changes but their hashes match #8463
• [22/n] [reconfigurator-cli] specify sled by serial number #8489
• [23/n] [reconfigurator-cli] allow setting sled policy in more situations #8491

TODO:

• Tests