Implement policy for managing docker build caches

[sxa]

Seen recently on test-azure-ubuntu2404-x64-1 but this is also a follow-on to #3007

https://docs.docker.com/build/cache/garbage-collection/ has some information on how the cache can be maintained. We should ensure that the amount of space used by docker is managed appropriately. I believe we have implemented some regular cleanups on some machines and we should ensure that we deploy this more universally - likely as part of the adoptopenjdk tags in the UNIX playbook. The test jobs are increasingly making use of docker, and so a certain amount of build up will occur and this needs to be managed.