When ./configure --disable-editable is in use (the default before #32406), the Sage library is installed using its custom incremental implementation of setup.py install -- which installs its files in site-packages and then removes the files that it does not know about (the "cleaner").

Problem 1: The cleaner is incompatible with namespace packages and trying to fix it would lead to complicated and awkward code (#32927). (Besides, setup.py install is deprecated since https://setuptools.pypa.io/en/latest/history.html#v58-3-0)

Problem 2: Because of the direct installation, we do not have wheels for sagemath-standard available (even if make wheels is used explicitly). Such wheels can be useful for making separate venvs.

In this ticket:

• We create a new option ./configure --enable-wheels (which can be used both with ./configure --enable-editable and ./configure --disable-editable).
• If enabled, installation of sagelib will go through wheel building and installation - like we do with all other Python packages. This enables modularized builds (Refactor sagemath-standard through sagemath-{categories,environment,repl} #34587).
• If disabled, there is no change.

A trivial ./sage -b is much slower with ./configure --disable-editable --enable-wheels compared to ./configure --disable-editable (from 28s as per timings in #32406 comment:21 to 70s).
This ticket brings a number of speed improvements to mitigate this.

CC: @jhpalmieri

Component: build

Author: Matthias Koeppe

Branch: 25898ba

Reviewer: Kwankyu Lee

Issue created by migration from https://trac.sagemath.org/ticket/32874