GitLab

in order to improve performance as 4 CPUs are available, recommendation
is "2x the number of CPUs available to the JVM", but 12 were assigned

This will improve performance as currently bots are fetching contents
from /changes which contains JSON data of patches, diffs as files and
archives which are generated on the fly, really nothing of relevance
to search engines.

In order to ease upgrades the optional declaration of the JRE/JDK
installation to use is removed:

https://gerrit-review.googlesource.com/Documentation/config-gerrit.html#container.javaHome

Switch to named volumes for cache, db, git, index and logs in order to
improve future compatibility with cloud services like Kubernetes. Move
etc and ssh from volumes to assets as they shall be versioned but
Gerrit may change contents. This means in future extra care has to be
taken when executing docker-build as changed contents inside the
container will be discarded.

Add a theme for PolyGerrit UI specifying a TYPO3 logo in the header,
"privacy policy" and "legal notice" links in the footer.

Remove theme definitions and files used for old GWT UI and the old
workaround to set the "Report Bug" URL for "legal notice".

Configuration to build and run the Gerrit 2.16.8 Ubuntu Docker image for
https://review.typo3.org based on the last state of the Chef cookbook
`site-reviewtypo3org`