A refinement of #32899, #32879:

sage.categories is a namespace package: The most basic categories needed for coercion are distributed in sagemath-objects; everything else in sagemath-categories.

However, we now declare imports from sage.categories.all to be OK.

Rationale: Categories are supposed to be abstract - so there should not be compile-time or module-load-time dependencies.

CC: @kwankyu @fchapoton @tscrim @tobiasdiez

Component: categories

Reviewer: Travis Scrimshaw

Issue created by migration from https://trac.sagemath.org/ticket/33202