Generalize page.on events

[ankur22]

What

Generalize page.on events architecture.

Why

So that new events can easily be added to the existing code.

Tasks

Beta Give feedback

1. Unify page.on event mappings #1473
   refactor tests +2
   
2. Refactor to type-safe page.on events #1474
   refactor +1
   
3. Refactor to type safe page.on event names #1477
   refactor +1
   
4. Refactor page.on mapping names #1478
   refactor +1
   
5. Streamline the addition and running of new page.on events #1475
   dx refactor +2
   
6. Refactor page.on event handling #1479
   refactor +1
   
7. Update k6 release notes and tasks

[inancgumus]

I've changed this issue's title to focus on the generalization of page.on as the total work is lengthy. Please revert if you think otherwise.

[ankur22]

During the PR to add page.on('metric') helpful comments were added which identified areas that could be refactored to work with generics:

• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Add page.on('metric') #1456 (comment)
• Another idea instead of generics: Add page.on('metric') #1456 (comment)