feat: allow EXTRA_JAVA_OPTS to be configured at runtime

[alir]

EXTRA_JAVA_OPTS is currently non-configurable and is added to CATALINA_OPTS at build time.

Users may want to configure the JVM heap values as well as some application properties at runtime, outside of the build process.

This change allows commands like the following to work:

docker run -p 8080:8080 -e "EXTRA_JAVA_OPTS=-Xmx2g" geoserver

This is picked up by Catalina when starting

and is also reflected in the GeoServer web console

[buehner]

Hi @alir . Thanks for the PR, but I do not understand the value your change adds as this feature is already available and working. Just try

docker run -it -p 80:8080 -e "EXTRA_JAVA_OPTS=-Xmx2g" docker.osgeo.org/geoserver:2.26.1 (so your change is not included) and it works out of the box.

In my eyes, there is no need to shift this to the startup script. In case you have a scenario where this is not working, please describe it and we can take this up again.