Replace SWT docker-images in platform.releng.aggregator by docker images from SWT repository

[HannesWell]

Currently there is a docker-image dedicated and used by SWT which is maintained in the platform.releng.aggregator repository:
https://github.com/eclipse-platform/eclipse.platform.releng.aggregator/tree/650d043c6efef7748dc6fb0c2aa4f0b66a8e5f45/cje-production/dockerfiles/centos-gtk4-mutter/9-swtBuild

And there is a Docker-image in the SWT repository for which I'm not aware of a user (it also seems not to be build and published):
https://github.com/eclipse-platform/eclipse.platform.swt/blob/8c39dcdfd2e28009e3866e61e1d40bf30d583c66/container/Dockerfile

My proposal is to remove unused images and to consider to maintain the image used by SWT (and Equinox) only in the SWT repository, to have it closer to the code that (mainly) uses it.

And since the centos-gtk4-mutter/9-gtk4 has a lot of lines in common with centos-gtk4-mutter/9-swtBuild I wonder if the latter could/should inherit from the former?