(from #29536)

This is like _recommended (from #29557), but for development tools.

Define a script package representing "useful stuff for Sage developers to have on a Docker image":

• include the stuff added in Add conda dev environment #33740 to environment-dev.yml
• include what is needed on VS Code devcontainers - Add devcontainer.json for development with VS Code in a Docker container #33671

We also use this package to define packages that would appear as "packages that developers should install" in
https://doc.sagemath.org/html/en/installation/source.html#linux-recommended-installation;
the new version from this ticket can be seen in https://c96c7c5813bd70d7b2d8d51135d57cc6acba18ad--sagemath-tobias.netlify.app/installation/source.html#system-specific-requirements

We also simplify the bootstrap-conda script and make it a bit faster.

Depends on #34301

CC: @tobiasdiez @dimpase @seblabbe @nbruin @egourgoulhon @slel

Component: packages: optional

Author: Matthias Koeppe

Branch/Commit: c39312c

Reviewer: Samuel Lelièvre

Issue created by migration from https://trac.sagemath.org/ticket/33851