Support Ubuntu 26.04

#### Description
The new Ubuntu LTS 26.04 (resolute) was released [last week](https://lists.ubuntu.com/archives/ubuntu-announce/2026-April/000323.html).

The github runner images should be available soon (https://github.com/actions/runner-images/issues/13964), but docker images are already available on [docker hub](https://hub.docker.com/_/ubuntu) (although still tagged as `devel`).

