Improve efficiency of running the most simple CI/CD builds
## Description
Slack: https://gitlab.slack.com/archives/C0SFP840G/p1681376329482399
We are still using a `ruby:3.1` image as a default one, even when someone does not specify an `image:` in their `.gitlab-ci.yml` at all.
It appears that we are not caching the image, because pulling it still takes 30+ seconds in a simple hello world build on GitLab.com:
```yaml
# .gitlab-ci.yml
hello:
script: echo "Hello World"
```
## Proposal
We should cache the default image and other, most popular ones by default, to reduce the time to start `script` block execution on shared runners.
**This may increase the speed of very simple builds by at least 50%.**
/cc @tmaczukin @clefelhocz1 @nicolewilliams
issue