scripts: elf_parser: added

Adds a python module intended to simplify other scripts that need to
work with device information compiled into the first pass `.elf` file.

Scripts utilizing this module can focus on iterating over dependency
graphs to generate the desired output, instead of also needing to
extract and build the graphs in the first place.

Signed-off-by: Jordan Yates <jordan.yates@data61.csiro.au>