The current solution to prebuild the gitpod docker image using github actions does not work nicely, since prebuilds triggered shortly after a new release still use the old gitpod image (and it may take up to a few days until the new image is available). This is especially notable for the develop branch, which is the default entry point if you want to start a new branch on gitpod.

In this ticket, we migrate the gitpod config to use the conda environment, which is now generally stable enough for serious development (e.g. almost all tests pass). As a positive side effect, the gitpod config simplifies and startup times are considerably reduced.

Depends on #33740
Depends on #33855

CC: @mkoeppe @dimpase @isuruf

Component: build

Author: Tobias Diez

Branch/Commit: 5748c21

Reviewer: Matthias Koeppe

Issue created by migration from https://trac.sagemath.org/ticket/33739