containers: Introduce a base image

Add a base image which all other images inherit from. This solves the
immediate problem of docker hub preventing us from pulling
debian:bookworm due to TOOMANYREQUESTS. The base image is now the only
image that pulls debian:bookworm and it will be rebuilt very
infrequently. Additionally, there is now a single place where we can
modify all images.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>