On GPUs which fail to initialize EGL, draw an error screen with Cairo

[YaLTeR]

Should turn on monitors as usual according to the config, then render and show a dumb buffer saying something like "Failed to initialize graphics acceleration. Press Super+Shift+E then Enter to exit niri." The target audience is: NixOS users with mesa version mismatch, NVIDIA users with old drivers, VM users who forgot to enable hw accel, kmsro users with the wrong device set in the config.