Conceptually we were trying to stuff subtly different actions into one vfunc:
* Read firmware from the device to update the verification checksums
* Read a firmware blob from the device for debugging
For the first action we might want to mask out the sections of the flash with
serial numbers (so the verification hashes match the ones published on the LVFS)
and for the second we want just a raw ROM file from the hardware with no
pre-processing that we can compare against an external SPI dumper.
Split out ->dump_firmware to get the raw blob, and allow plugins to also
implement ->read_firmware() if they have to mask out specific offsets or remove
specific images from the FuFirmware container.
In the common case when masking is not required, fall back to using a 'binary'
FuFirmware automatically to make most plugins simpler.
If we say that the version format should be the same for the `version_lowest`
and the `version_bootloader` then it does not always make sense to set it at
the same time.
Moving the `version_format` to a standalone first-class property also means it
can be typically be set in the custom device `_init()` function, which means we
don't need to worry about *changing* ther version format as set by the USB and
UDev superclass helpers.
We don't actually need either of the things it provides (looking up in source
and built, and converting to an absolute path) so just replace it with
g_build_filename() instead.
This also has the advantage that it does the right thing on Windows.
The new plugin is called `optionrom` as this is the only type of image that it
parses for verification only. FuUdevDevice is also the generic parent already.
