Drop support for older OS in the next major release

[jasontedor]

The following OS have or will soon see their end-of-life. Therefore, Elasticsearch will drop support for these OS in its next major release:

• CentOS 6 (November 30, 2020)
• Oracle Enterprise Linux 6 (March, 2021)
• Ubuntu 16.04 (April, 2019, security updates end in 2021)
• openSUSE Leap 42 (June, 2019)
• Debian 8 (June 30, 2020)
• Amazon Linux (June 30, 2020)

[elasticmachine]

Pinging @elastic/es-core-infra (:Core/Infra/Packaging)