Set the new active slot on post_update for RoT updater

[karencfv]

We want to add a step to set the new active slot during the post_update.

This could be a little tricky since we need to wait for the RoT to be back online after it's reset.

The reset takes a few seconds, I believe the best way to check that a reset has been successful is by checking boot_info. This should be updated with the information from the update once it's ready.

Then we can set the device as the active slot

Related: #7989