(from #29941, #33800)

These distributions do not need ECL, so we revise the unconditional dependency of sage.env.cython_aliases on ecl-config introduced in #30770.

We add some missing modules to the MANIFEST of sagemath-objects.

To test:

 ./bootstrap && ./sage -sh -c '(cd pkgs/sagemath-objects && SAGE_NUM_THREADS=16 tox -r -v -v -v -e py39)'

CC: @dimpase @kwankyu @tobiasdiez

Component: distribution

Author: Matthias Koeppe

Branch/Commit: c5d43bd

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/33803