Reevaluate browser configuration

[ankur22]

We want to make it simpler for the user to work with the browser, so that they don't need to worry about the lifecycle of the browser and to help us with the end goal of abstracting away the confusing browserContexts object.

This issue is to evaluate and prove that we can isolate and abstract the browser from the end user for majority of use cases. Some use cases will still require the configuration of the browser which we have a plan for too.

Tasks

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1. Evaluate Browser params #856
   team/k6browser +1
   
2. Evaluate move of slowMo and timeout browser options to browser context #857
   poc team/k6browser +2
   
3. Work with VU.State.Options to validate browser options #858
   enhancement ux +2
   
4. Do not apply browser timeout option as default navigation timeout #864
   breaking +1
   
5. Parse browser options from ENV #874
   breaking +1
   
6. Do not expose browser slowMo option #875
   breaking +1
   
7. Remove browser devtools option #867
   breaking +1
   
8. Remove browser env option #869
   breaking +1
   
9. Remove browser proxy option #871
   breaking +1