Support multiple fstab configs for one mount point

This allows us to mount with such fstab:
/dev/block/by-name/system /system ext4  ro slotselect
/dev/block/by-name/system /system erofs ro slotselect
This will be used when mount partition through ensure_path_mounted
in recovery.

Bug: 195726623
Test: mount with different image on the same fstab
Change-Id: I7761489a3e2bf46331563e872b6dfaa8b685a082
Signed-off-by: Huang Jianan <huangjianan@oppo.com>