Create Blivet standard partitioning with ext4 testcase.
    
    This PR introduces a test case that uses the Blivet partitioning
    tool to create a standard partitioning layout with / and /boot
    (and specific partitions for UEFI and ARM64) using ext4 as
    the selected filesystem.
    
    It also adds a postinstallation test to check that the partitions
    have been created correctly.