Add possibility to override ephemeralStorageSizeInGiB from declarative

[Koziol-ku]

What feature do you want to see added?

There is no possibility to override ephemeralStorageSizeInGiB using declarative pipeline syntax like

 agent {
        ecs {
            inheritFrom 'example-agent'
            cpu 1024
            memory 2048
            ephemeralStorageSizeInGiB 50
            image 'jenkins/inbound-agent:latest'
            }
        }

It's pretty easy to add this functionality as it's already done for scripted pipelines.

Upstream changes

No response