[USETUP] Improve the formatter & check-disk state machine. CORE-7749
- Find or set the active system partition only once, when we start the
formatting stage. If the system partition is to be created in some
non-partitioned space, we create it.
- A file-system check is always scheduled for both the system and the
installation partitions.
- If the system partition was already formatted (which usually means
that it already existed on the system), don't ask for formatting it.
CORE-13205
- For each partition to be formatted, the file-system menu list is
re-created, in order to display only the FSes that are compatible
with the selected partition, and allow to give the user the choice
to keep the existing file-system only if the selected partition was
already formatted.
- Check whether the user attempts to delete the partition on which
the installation source is present, only if it is not "new" and is
formatted.
- Check first whether the current partition is the system partition,
before displaying the CONFIRM_DELETE_SYSTEM_PARTITION_PAGE.