This change removes the XPackExtension mechanism in favor of
SecurityExtension that can be loaded via SPI and doesn't need
another (duplicate) plugin infrastructure
Original commit: elastic/x-pack-elasticsearch@f39e62a040
This commit moves the source file in x-pack-core to a org.elasticsearch.xpack.core package. This is to prevent issues where we have compile-time success reaching through packages that will cross module boundaries at runtime (due to being in different classloaders). By moving these to a separate package, we have compile-time safety. Follow-ups can consider build time checking that only this package is defined in x-pack-core, or sealing x-pack-core until modules arrive for us.
Original commit: elastic/x-pack-elasticsearch@232e156e0e
Simon Willnauer
Jason Tedor
Ali Beyad