Source dir cleaner for editable installs

[mkoeppe]

We implement a simple version of sage_setup.clean.clean_install_dir for editable installs: Remove .so files and .pyc files that are leftovers from other branches, i.e., there is no corresponding source file (.pyx for .so; .py for .pyc).

This fixes incremental builds when a Cython module is replaced by a Python module of the same name, as noted in #34324 comment:3

This simple version, because it is only applied to the source directory, not an installation directory, will be safe for modularization (in contrast to clean_install_dir, see #32927).

CC: @kwankyu

Component: build

Issue created by migration from https://trac.sagemath.org/ticket/34334

[mkoeppe]

comment:1

To be checked whether it's needed at all when we switch to PEP 660 editable wheels (#34209)

[videlec]

Is that also a problem when removing a Cython module?