The artifact resolver of the Docker test framework does not use the proxy configured for the JVM

The Docker-based functional test framework resolves the artifacts of the tested XWiki instance (the WAR dependencies and the extensions to install) with its own Maven Resolver session, in RepositoryResolver. That session has no proxy configured, so the artifacts are always downloaded without a proxy, even when the JVM running the tests is configured to use one (with the https.proxyHost, https.proxyPort and http.nonProxyHosts system properties, e.g. through JAVA_TOOL_OPTIONS).

When the remote Maven repositories can only be reached through a proxy, the functional tests fail during the setup as soon as an artifact (or a newer SNAPSHOT build listed in the local metadata) is missing from the local repository, while Maven itself downloads it fine:

Could not transfer artifact org.xwiki.platform:xwiki-platform-notifications-filters-default:pom:18.10.0-20261030.203932-42 from/to xwiki-snapshots (https://nexus-snapshots.xwiki.org/repository/snapshots/): nexus-snapshots.xwiki.org
Caused by: java.net.UnknownHostException: nexus-snapshots.xwiki.org

The resolver should use the proxy configured for the JVM, which Maven Resolver supports with its JreProxySelector.