sage.structure, sage.misc: Replace import of sage.categories.all by more specific imports #29916
Description
sage.structure should only depend on basic categories such as sage.categories.morphism, sage.categories.pushout to support the parent/element framework and coercion, but not on more specialized ones such as sage.categories.modular_abelian_varieties.
This is for #29865 (sage-objects), which should pull in only a small part of sage.categories -- less than what sage.categories.basic imports.
Component: categories
Author: Matthias Koeppe
Branch/Commit: ce8fa70
Reviewer: Travis Scrimshaw
Issue created by migration from https://trac.sagemath.org/ticket/29916