This commit defines a new ROMFS filesystem for storing read-only files that
can be memory mapped, and a new VfsRom driver. Files opened from this
filesystem support the buffer protocol. This allows naturally getting the
memory-mapped address of the file using:
- memoryview(file)
- uctypes.addressof(file)
Furthermore, if these files are .mpy files then their content can be
referenced in-place when importing. Such imports take up a lot less RAM
than importing from a normal filesystem. This is essentially dynamically
frozen .mpy files, building on the revamped v6 .mpy file format.
Signed-off-by: Damien George <damien@micropython.org>
