Today we enable users to customize the environment through the use of
ES_INCLUDE. This made sense for legacy reasons when we did not have
nicities like jvm.options (so dumped JVM options in the default include
script) and somewhat duplicates some of the functionality that we will
need from a dedicated environment script. This commit removes support
for ES_INCLUDE as a first step towards a dedicated include script.
Relates #25804
67a4288c9a