Making `k6/experimental/browser` module part of k6 core

[ankur22]

What

Migrate the browser module out of experimental:

k6/experimental/browser -> k6/browser

Why

For this to be achievable the aim is to make the browser module:

1. stable during the runtime;
2. have a stable API.

Some of our users will not want to work with an experimental module with the fear that the cost of maintaining many scripts and breaking changes out weighs the pros of working with the browser module. Graduating the browser module out of experimental will signal to those users that:

1. The APIs are backwards compatible, and the upmost effort will be put into ensuring we don't break this;
2. No major breaking changes are coming to the APIs;
3. There are no known major issues.

Blockers

We need to finalize and possibly work on the following points before we can be ready to graduate browser out of experimental:

Tasks

Preview Give feedback

1. Browser v2: Async APIs #428
   23 of 23
   async epic feature playwright +4
   

   
2. Browser: Runtime stability k6#4236
   area: browser triage +2
   
3. Migrating to k6-core's linter #1292
   0 of 4
   ci compatibility security +3
4. Update the roadmap.
5. Is xk6-browser going to support multiple browsers other than chromium/chrome?
6. Are there any major refactors coming up that could destabilize the module?
7. How will k6 v1 affect browser module's stability?
8. Should browser options be shortened (#3310)? Not now, we need more feedback.
9. Do all xk6-browser APIs need to be converted to async? Yes they do
10. Does xk6-browser need to be more compatible with Playwright APIs?
11. If we haven't reached enough of a compatibility with Playwright, what is enough?
12. Are we expecting any major breaking changes?
13. Are there any major issues that must be resolved (e.g. #971)?

[inancgumus]

Closed by grafana/k6#3793