New function _get_info_image reads values from the distribution ini configuration files stored in image/dists
This simplifies the code and avoids having logic for different versions in multiple functions.
The ini format is as follows - it may change and be extended in the future.
The filename is the dist name that is passed into the building functions.
The current images now have a prefix "rpios-"
* name: name of distro - eg buster
* version: rpios/debian version
* url: url for image file
* format: format of the image file - currently supported is zip and xz (used by raspberrypi.org)
* platforms: list of the platforms supported (eg. rpi1 rpi2 rpi3 rpi4)
* file_PLATFORM (name to be used in the image file for each platform)
* title_PLATFORM (user friendly name of file for each platform - used for rpi imager json)
