Understand and document docker update policy

We had an incident recently where a [critical openssl update](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-0286) which was [released by Ubuntu on the 6th February](https://launchpad.net/ubuntu/+source/openssl/3.0.2-0ubuntu1.8) did not make it into our container images for almost a month (1st March).

This was discussed in [this slack thread](https://adoptium.slack.com/archives/CSJ203YTW/p1676891087242629) and while the current images are now correct with libssl3 package `3.0.2-0ubuntu1.8` we should:

- Understand why there was such a delay in getting a rebuild with this patched openssl into our images (which are based on the official images)
- Create a [FAQ entry](https://adoptium.net/docs/faq/) to describe the update process and the reasons why there might be a delay plus set any expectations around this.

Notes for reference (I'm not an expert on the base image update process so I cannot comment on the implications of these but it is just from some observations:
- https://git.launchpad.net/cloud-images/+oci/ubuntu-base/log/?h=oci-jammy-22.04 suggests there was an update to the base image on the 7th and 17th of February and then another on the first of March. I would have expected all three of those to have included the update
- Having said that, https://git.launchpad.net/cloud-images/+oci/ubuntu-base/log/?h=jammy-22.04 does not indicate there was a manifest update around that time
- Our `eclipse-temurin:17-jre` was confirmed to have been rebuilt around the 16th February with a vulnerable openssl based on the comments in the thread.
- The images pushed yesterday (March 2nd) have the patched versions of libssl3