feat(cgpt): Add min_size argument to OpenDrive()

This enables the caller to either assert the drive is a given size,
extend existing image files to the given size if mode is O_RDRW, or
create new image files if mode is O_RDRW | O_CREAT.

All calls to OpenDrive have been updated to pass a min_size of 0,
preserving the existing behavior.
11 files changed