Cleanup confirm_blob & related code

[ibz]

There have been a lot of discussions around confirm_blob, confirm_action, warnings and related code. Some of the more serious issues have been fixed, but it is time to take a step back and refactor this part of our code base once for all, especially since the upcoming FirmwareUI API will demand more consistency here.

Let's centralize all tasks below:

• unify warning_hi_prio across models
• T3B1: make warning_hi_prio cancelable
• drop text_mono from confirm_blob
• drop info from confirm_blob
• drop hold from confirm_blob
• confirm_blob_intro: is there a better way to do this?
• rename ConfirmBlobParams.cancel to something else
• look into menus that have just "cancel" as a menu item

PS: This will be an on-going effort, perhaps split into multiple unrelated PRs, but let's keep it concrete and actionable.