feat: create sparse images

Instead of allocating the whole image on the disk, only allocate the parts that actually contain data. This reduces the required disk space to store or create images.

Changelog: Title
Ticket: None

modules/disk.sh

@@ -60,7 +60,7 @@ disk_get_part_nums() {
 #  $3 - size (in 512 blocks)
 #  $4 - path to output file
 disk_extract_part() {
-    run_and_log_cmd "dd if=$1 of=$4 skip=${2}b bs=1M count=${3}b status=none iflag=count_bytes,skip_bytes"
+    run_and_log_cmd "dd if=$1 of=$4 skip=${2}b bs=1M count=${3}b status=none conv=sparse iflag=count_bytes,skip_bytes"
 }
 
 # Convert MiB to number of 512 sectors
@@ -98,7 +98,7 @@ disk_align_sectors() {
 # $2 - destination file
 # $3 - offset in number of 512 sectors
 disk_write_at_offset() {
-    run_and_log_cmd "dd if=${1} of=${2} seek=${3} conv=notrunc status=none"
+    run_and_log_cmd "dd if=${1} of=${2} seek=${3} bs=512 conv=notrunc,sparse status=none"
 }
 
 # Create file system image from directory content