Add playwright concurrency - multi-user mode

[webfiltered]

Requires: Comfy-Org/ComfyUI_devtools#3

Changes testing mode to per-file concurrency - each file runs its contents sequentially. Some tests explicitly rely on the state from the previous test.

The ComfyUI test instance must have --multi-user set, or tests will fail randomly (polluted state).

[huchenlei]

Hmmm, Duplicated Username?

[webfiltered]

Comfy-Org/ComfyUI_devtools#3 - probably should have linked the PRs.

[webfiltered]

Looks like it's not getting the --multi-user on the command line:

✓ built in 7.96s
Run python main.py --cpu  &
  python main.py --cpu  &
  wait-for-it --service 127.0.0.1:8188 -t 600
  shell: /usr/bin/bash --noprofile --norc -e -o pipefail {0}