Implement NVS Partition Facility

[DaneSlattery]

It would be useful to not have multiple separate tools that need to interact to create images. This tool already supports converting elf to bin, csv to bin, now we could support generating data partitions:

https://docs.espressif.com/projects/esp-idf/en/stable/esp32/api-reference/storage/mass_mfg.html
or

[DaneSlattery]

It would also be incredibly useful to be able to write postcard structs into this nvs image directly.

[juliankrieger]

Are there any pointers on where to begin for this issue? I would be happy to contribute.