Improve browser close detection constant timeout

[inancgumus]

Originally posted by @inancgumus in grafana/xk6-browser#1442 (comment)

https://github.com/grafana/xk6-browser/blob/aa6a1c0947b90af1cefa70519722322cc7201b73/common/browser.go#L539-L552

I worry that we would need to change this whenever a larger timeout is needed. A larger timeout can cause prematurely aborted errors from the engine team. Two hopefully possible solutions:

• Implementing our own Context implementation that automatically cancels when the process is dead
• Making this an environment variable