[js/webgpu] use Headless for webgpu test by default (#19702)
### Description
use Chromium Headless for webgpu test by default. Still use normal
Chromium with window when debug=true or perfMode=true.
Use the
[`--headless=new`](https://developer.chrome.com/docs/chromium/new-headless)
mode.
### Motivation and Context
try to use a more stable way to launch npm tests to avoid a "chrome not
found" issue in pipeline, which may potentially caused by windowed
application.