rauc: improve upgrade output

[rical]

Description

Add two patches which improve upgrade output.

0003-src-install-print-bootname-when-checking-slot.patch

Prints the bootname during slot probing. This patch is sent upstream but not reviewed yet.

 40% Updating slots
 40% Checking slot rootfs.1 (secondary)
 46% Checking slot rootfs.1 (secondary) done.
 46% Copying image to rootfs.1

0004-src-main-add-warning-banner-at-start-of-installation.patch

Print a "standard warning banner" at start of install.

rauc install tftp://192.168.122.1/infix-x86_64.pkg
+------------------------------------------------------------------------------+
|                                                                              |
|      [!] Installation might take a while. DO NOT power off the device.       |
|                                                                              |
|                   Please wait while the upgrade completes.                   |
|                                                                              |
+------------------------------------------------------------------------------+
installing
  0% Installing
  0% Determining slot states
 10% Determining slot states done.

Checklist

Tick relevant boxes, this PR is-a or has-a:

• Bugfix
  • Regression tests
  • ChangeLog updates (for next release)
• Feature
  • YANG model change => revision updated?
  • Regression tests added?
  • ChangeLog updates (for next release)
  • Documentation added?
• Test changes
  • Checked in changed Readme.adoc (make test-spec)
  • Added new test to group Readme.adoc and yaml file
• Code style update (formatting, renaming)
• Refactoring (please detail in commit messages)
• Build related changes
• Documentation content changes
  • ChangeLog updated (for major changes)
• Other (please describe):

[troglobit]

Nice work on this! Appreciate the effort to upstream as well 👏