Ubuntu 26.04 support

[theboringstuff]

Description

New Ubuntu 26.04 is released, we need to support it

Solution

• Removed Ubuntu 20.04 support as it has reached EOL https://ubuntu.com/about/release-cycle
• Added Ubuntu 26.04 support
  • Made it a separate "os family" in KubeMarine, because it requires different version of containerd/haproxy
  • Ubuntu 26.04 uses chrony and has specific config location for it https://documentation.ubuntu.com/release-notes/26.04/summary-for-lts-users/#chrony
  • last command was removed from Ubuntu by default, so changed all places from last reboot to uptime -s
  • rust implementation of dd command on Ubuntu 26.04 has a bug, so dd usage was replaced with read
    • dd iflag=nonblock doesn't work with stdin (fd 0) uutils/coreutils#11543
  • rust implementation of sudo seem to have bug, it hangs on certain commands (check_paas etcd health check, specifically), so for ubuntu26.04 sudo was set back to previous C implementation using update-alternatives
    • https://documentation.ubuntu.com/release-notes/26.04/summary-for-lts-users/#sudo-rs
    • https://ubuntu.com/server/docs/how-to/security/user-management/#sudo-rs
  • added PAGER=cat header for apt commands, because on ubuntu26.04 apt show now shows output with pager, which hangs KubeMarine commands infinitely
    • this is probably due to apt v3 update https://documentation.ubuntu.com/release-notes/26.04/summary-for-lts-users/#package-management-apt-3
• Fixed issue with backup procedure, previously it did not backup node files after encountering first non-existing file
• Updated tests accordingly
• Updated docs accordingly

Test Cases

1. Try installing cluster on Ubuntu 26.04, configure chrony instead of timesyncd, make sure installation passes and chrony task succeeds. Run check_paas/check_iaas, make sure they succeed. Make sure containerd version is 2.2.* and haproxy is 3.*
2. Try backup procedure with Ubuntu 26.04, make sure /etc/chrony/chrony.conf file is present in archive
3. Make sure KubeMarine continue to work with other OSes (except Ubuntu 20.04, which is removed). Make sure containerd/haproxy versions do not change for other OSes

Checklist

• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• There is no breaking changes, or migration patch is provided
• Integration CI passed
• Unit tests. If Yes list of new/changed tests with brief description
• There is no merge conflicts