Stop depending on BASE_IMAGES_DIGESTS TaskRun result

[zregvart]

The BASE_IMAGES_DIGESTS TaskRun result will be deprecated and removed.

We have the base_image_registries.base_image_info_found rule that checks that the BASE_IMAGES_DIGESTS TaskRun result is provided, we most likely need to remove that part of the rule and adjust the documentation. As well as fetching the base image information via that result.

[lcarva]

We should definitely do that for clean up purposes. 👍

I just want to clarify that all the rules in that package should handle the case where that result is not specified. base_image_registries.base_image_info_found for example will only emit a violation if the result is not found and no sboms were also found.