Upgrade to the latest ELK OSS release. Due to the licensing change, this
effectively pins us to 7.10.x which is supported until 2022-05-11 [1].
This patch also takes advantage of the ARM artifacts which have
been kindly provided since the 7.8.0 release [2].
[1] https://www.elastic.co/support/eol
[2] https://www.elastic.co/blog/elasticsearch-on-arm
Change-Id: Icfa3db5788b25f70ee75411dbaf20d8d4a6a734b