This patch uses the newly-added esp32.Partition class to replace the
existing FlashBdev class. Partition objects implement the block protocol
so can be directly mounted via uos.mount(). This has the following
benefits:
- allows the filesystem partition location and size to be specified in
partitions.csv, and overridden by a particular board
- very easily allows to have multiple filesystems by simply adding extra
entries to partitions.csv
- improves efficiency/speed of filesystem operations because the block
device is implemented fully in C
- opens the possibility to have encrypted flash storage (since Partitions
can be encrypted)
Note that this patch is fully backwards compatible: existing filesystems
remain untouched and work with this new code.