Breaking: upgrade to abstract-level 3

[vweevers]

No description provided.

[vweevers]

Blegh, fails on some unrelated electron thing:

Command: npm run test-electron
/usr/bin/xvfb-run --auto-servernum npm run test-electron

> classic-level@2.0.0 test-electron
> electron test/electron.js

[3550:0[12](https://github.com/Level/classic-level/actions/runs/12976869518/job/36189627026?
pr=112#step:8:13)6/173356.437754:FATAL:setuid_sandbox_host.cc(158)] The SUID sandbox helper binary was
found, but is not configured correctly. Rather than run without sandboxing I'm aborting now. You need to
make sure that /home/runner/work/classic-level/classic-level/node_modules/electron/dist/chrome-sandbox
is owned by root and has mode 4755.
/home/runner/work/classic-level/classic-level/node_modules/electron/dist/electron exited with signal
SIGTRAP
/usr/bin/bash /home/runner/work/_actions/GabrielBB/xvfb-action/v1/cleanup.sh
No xvfb processes to kill
Error: The process '/usr/bin/xvfb-run' failed with exit code 1

[vweevers]

The solution is to lift the restrictions that Ubuntu 24.04 implements in the AppImages.

sudo sysctl -w kernel.apparmor_restrict_unprivileged_userns=0

electron/electron#42510 (comment)

It seems ill-advised and a bit silly to disable an OS security feature in order to enable an Electron security feature (sandboxing) but should be okay to do this in our GHA workflows. At least until Electron has an official solution.