recursive_fill_list() is used to order Requires and Requires.private,
but it relied on fill_one_level() to make the list adjustments as it
descended the package tree. There were two issues with this approach:
1. It added all the dependencies from a package immediately rather than
descending through each dependency first. This made it sort of mix
between depth- and breadth-first resolving.
2. It did not add the requested package to the list, forcing the caller
to add it.
This simplifies the code so that it descends all the way to the least
dependent package and prepends them as it unwinds. This ensures the
ordering will be sorted from most dependent to least dependent package.
Ordering of -l flags is corrected by a later sorting, but this fixes
ordering on non-l flags. Add a new test specifically for non-l Libs
flags.
Freedesktop #34504
