This has been available since 9.3, has been improved in 9.4 and in the 9.7 series (#33855), and is ready for general consumption

Introduction:

• https://wiki.sagemath.org/ReleaseTours/sage-9.3#Editable_.28.22in-place.22.2C_.22develop.22.29_installs_of_the_Sage_library

Discussion:

• https://groups.google.com/g/sage-devel/c/0GV8_O1VwbI

Depends on #32672
Depends on #33855
Depends on #31049
Depends on #33627

CC: @kliem @dimpase @orlitzky @tobiasdiez @saraedum @kiwifb @jhpalmieri @williamstein @nbruin

Component: build

Author: Matthias Koeppe

Branch/Commit: a911e0f

Reviewer: John Palmieri

Issue created by migration from https://trac.sagemath.org/ticket/32406