Old-style SPKGs were deprecated in #19158, merged in Sage 6.9.

There is only sparse evidence of non-broken old-style SPKGs:

• cunningham_tables - https://groups.google.com/d/msg/sage-support/T4IO-AmOsCM/HYy_N6UdAQAJ - added as new-style package in convert cunningham_tables to a new style package #29834

• polytopes_db_4d - added as new-style package in polytopes_db_4d converted to new style package #26029

We remove support for old-style packages, but we keep the command sage -p, which can also be used for installing a new-style package without dependencies.

Depends on #26029
Depends on #29834

CC: @dimpase @embray @vbraun @jhpalmieri @orlitzky

Component: build

Author: Matthias Koeppe, John Palmieri

Branch/Commit: c0fb6d4

Reviewer: Dima Pasechnik, John Palmieri, Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/29289