[][OpenWrt Dev][Add dual-boot features for fstools]

[Description]
Add a new feature for fstools that disables splitting rootfs_data partition
from rootfs partition for rootdisk-type devices.
Also add partition key parsing support (PARTUUID=/PARTLABEL=)

[Release-log]
N/A

Change-Id: Id57707c9b586fc5acdca416e114bdd4dbeadd0f4
Reviewed-on: https://gerrit.mediatek.inc/c/openwrt/feeds/mtk_openwrt_feeds/+/5595597
3 files changed