refa(devcontainer): rework to use mise for fast switching

[solnic]

This rework comes with 3 nice improvements:

1. Mise for fast switching between modern ruby versions (including jruby)

The image by default ships with the latest ruby (4.0.3 at the moment), and then switching to older rubies is super easy:

➜  sentry git:(refa/rework-devcontainer) ruby -v            
ruby 4.0.3 (2026-04-21 revision 85ddef263a) +PRISM [aarch64-linux]
➜  sentry git:(refa/rework-devcontainer) mise shell ruby@3.4
ruby@3.4.9      extract ruby-3.4.9.arm64_linux.tar.gz                                                                                                    ✔
➜  sentry git:(refa/rework-devcontainer) ruby -v 
ruby 3.4.9 (2026-03-11 revision 76cca827ab) +PRISM [aarch64-linux]
➜  sentry git:(refa/rework-devcontainer) mise shell ruby@jruby
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 38.8M  100 38.8M    0     0  86.2M      0 --:--:-- --:--:-- --:--:-- 86.4M
ruby@jruby-10.1.0.0 ==> Installed jruby-10.1.0.0 to /home/sentry/.local/share/mise/installs/ruby/jruby-10.1.0.0                                          ✔
➜  sentry git:(refa/rework-devcontainer) ruby -v
jruby 10.1.0.0 (4.0.0) 2026-04-20 32f988b78c OpenJDK 64-Bit Server VM 21.0.11+10-LTS on 21.0.11+10-LTS +indy +jit [aarch64-linux]

All that in less than 20s.

For legacy Rubies, we still use dedicated dev container builds, no way around this.

2. Improved e2e spec setup in CI

Supports running against 4.x and 3.x rubies and uses pre-built images from the build_images workflow. We also no longer depend on foreman for running e2e test apps, and instead we just use mise scripts.

3. Versioned dev container images with workflow manual trigger enabled

Our build images workflow publishes versioned images based on .devcontainer/VERSION so it's easier to maintain this setup now. Especially when a topic branch is used to make some tweaks, like this very PR/branch.

[dingsdax]

lgtm