* Remove log4j dependency from elasticsearch-core
This removes the log4j dependency from our elasticsearch-core project. It was
originally necessary only for our jar classpath checking. It is now replaced by
a `Consumer<String>` so that the es-core dependency doesn't have external
dependencies.
The parts of #28191 which were moved in conjunction (like `ESLoggerFactory` and
`Loggers`) have been moved back where appropriate, since they are not required
in the core jar.
This is tangentially related to #28504
* Add javadocs for `output` parameter
* Change @code to @link
This is related to #27933. It introduces a jar named elasticsearch-core
in the lib directory. This commit moves the JarHell class from server to
elasticsearch-core. Additionally, PathUtils and some of Loggers are
moved as JarHell depends on them.
Lee Hinman
Adrien Grand
Tim Brooks