Send JES events as "job executor using $IMAGE" events

[agardnerIT]

Currently every job that JES runs has a .started and .finished name as "job executor service".

It would be really nice to see that JES is being used to run X container image.

So rather than job executor service started we see something like alpine/helm:3.7.2 by job executor service started

[Raffy23]

I think that it's a good idea to add more information to the started event, but we probably can't just directly include the images in the message, because the job-executor can start multiple named actions, which can contain multiple named tasks. So we can potentially run multiple images in one .started event.

But besides that, I'm currently not sure if we can attach the required information to a .started event, such that it will be displayed correctly in the UI.

[christian-kreuzberger-dtx]

That would be information we could add to a .status.changed event within the message. See keptn/spec/CloudEvents.md for reference of this type.