feat(playwright): reuse existing server

[Barbapapazes]

related to #803

Hello 👋,

I was trying this module to write tests cause I really think tests are important.

But, in development, this module, e2e with Playwright, is slow. So slow that it creates too much friction to write tests and I think a lot of people will give up on writing tests because of that.

In the meantime, I use Playwright at work for e2e testing on an Angular app and it's fast. It's faster than unit tests with Jest and it's possible make test-first development with it.

After deep diving into the module, I found that for each test and each run a new app is built and started. This is the main reason for the slowness. While I understand this behavior on a CI pipeline, I don't think it's necessary on development. This is too much overhead for a little (or no) gain.

So I added a new option (similar to the existing one in Playwright, https://playwright.dev/docs/test-webserver#configuring-a-web-server) to reuse a dev server for all tests. This speeds up the tests a lot and makes it possible to use test-first development with Playwright.

While writing this, I realized that it could be possible to reuse the existing options instead of add a new one in the use.nuxt object. I'll try to do that in this PR. => this does not seems possible microsoft/playwright#7267

Maybe we could just disable the Nuxt integration to be able to reuse existing options

[Barbapapazes]

Hey 👋, @danielroe, I think this PR is ready for review. I put 2 todos inside the code that are more questions than todos. I'd like to hear what you think.