Update docker base image to ubuntu 24.04

[r4victor]

• Updates dstack's docker images to ubuntu 24.04.
• Removes subversion and mercurial (74MB installed).
• Updates nvidia keyring installation as apt-key was deprecated.
• Drops dockerfile-plus (external dependency) in favor of docker buildx build --target
• Changes dstack user uid/guid from 1000 to 1001 as ubuntu 24 now ships ubuntu user with uid 1000 (the dstack user is not yet used by dstack).