Retrieves all diagonals of a two dimensional array (which have differing
lengths). Useful to solve e.g. Project Euler problem 11
(<https://projecteuler.net/problem=11>).
Change-Id: I853bc6eaaf869326d84d8e789fee9995f5a332d8
Reviewed-on: https://cl.tvl.fyi/c/depot/+/12897
Autosubmit: sterni <sternenseemann@systemli.org>
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>