feat: add option to preserve user partition

[MatteoPologruto]

Add a flag to the flash command to allow the user to preserve the home partition. When the flag (for example --preserve-user) is passed to the command, the Flasher CLI should:

1. check if the current image on the board supports home partition preservation (so it's not a R0 image)
2. check if the target image has the file rawprogram0.nouser.xml
3. warn the user when one of the above fails and a complete flash is required, otherwise procede with the flash preserving user partition

Steps to check if the current image is R0:

1. create a read.xml file

<?xml version="1.0" ?>
<data>
 <read SECTOR_SIZE_IN_BYTES="512" filename="dump.bin" physical_partition_number="0" num_partition_sectors="19" start_sector="1"/>
</data>

2. run qdl --storage emmc prog_firehose_ddr.elf read.xml. NOTE: prog_firehose_ddr.elf does not have to be the one from the original image on the board
3. run xxd dump.bin | less to examine the resulting file
4. count the partitions, starting from the address 0x200 with an offset of 80h: if the number of entries in the GPT, stored in 4 bytes starting at the address 0x50 is 76 and the actual number of partitions is 73, then the image is R0

Related issue: Move examples (and other data) out of the Arduino home folder