It is just a copy-paste of "dijkstra" but the name
implies what it actually is. Not an implementation of minimum cost path
Dijkstra algorithm, but a helper data structure.
I keep the old "dijkstra.h/c" files for the moment to avoid breaking the
current code.
Changelog-EXPERIMENTAL: askrene: add priorityqueue
Signed-off-by: Lagrang3 <lagrang3@protonmail.com>