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)
• [x] 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):