CLI flag to choose whether to open a new lighthouse page or not

[Shivam93937]

Feature request summary

A CLI flag (something like --reuse-page) to re-use the existing page that was running on the browser that puppeteer connects to.
The page can be selected from await lhBrowser.pages().

Are you willing to work on this yourself?
Yes

What is the motivation or use case for changing this?
It will help run lighthouse programmatically inside applications like CEF and Electron where opening a new page (by default) causes a failure when connecting to it through remote debugging port.

How is this beneficial to Lighthouse?
It will widen the audience to which lighthouse can be used and increase the tool's users.

Mentioned the changes in the screenshot:

[adamraine]

This should be possible already with the Node API: https://github.com/GoogleChrome/lighthouse/blob/main/docs/puppeteer.md#option-1-launch-chrome-with-puppeteer-and-handoff-to-lighthouse

Is there a use case where you need to use the CLI and can't use the Node API?