Implement V1 API for eventing.* resources.

[vaikas]

Problem
Add V1 api for eventing.*

As discussed today, we'll break the tasks down by the api group. This issue tracks the work for that. Also as discussed in the meeting, I offered to jot down some representative PRs that are necessary for the work, and hopefully will help folks doing the work:
Introduce types:
#2407

Defaulting webhook:
#2645

Conversions:
#2611
(but since the functions were renamed, so need to use these names):
#2632

That's a start, I might be missing something but figured I'd share some resources so folks can get started :)

[matzew]

For Trigger, there is the discussion, to introduce some sort of EL for v1. /cc @grantr @slinkydeveloper

[slinkydeveloper]

@grantr I can open a new issue and start investigating on it, is that ok for you?

[aliok]

/assign

let me do the type bumping

[slinkydeveloper]

Opened an issue for the trigger EL thing #3359