Create an offline snapshot for air-gapped installation docs

[KOTungseth]

Why?

We have a group of customers that need to view all air-gapped installation docs in a single location. Since these customers don't have access to public internet, we should provide them with an offline snapshot of these air-gapped install docs.

Existing air-gapped installation docs and current owners

• Logstash (David K and Karen): https://www.elastic.co/guide/en/logstash/8.5/plugins-filters-geoip.html#plugins-filters-geoip-manage_update
• Logstash maybe (David K and Karen): https://www.elastic.co/guide/en/logstash/current/offline-plugins.html
• Fleet and Elastic Agent Guide (Karen): https://www.elastic.co/guide/en/fleet/current/air-gapped.html
• Fleet and Elastic Agent (Karen): https://www.elastic.co/guide/en/fleet/7.17/fleet-overview.html#package-registry-intro
• Elastic Cloud on Kubernetes (Arianna): https://www.elastic.co/guide/en/cloud-on-k8s/master/k8s-air-gapped.html
• ECE (Arianna): https://www.elastic.co/guide/en/cloud-enterprise/3.5/ece-install-offline.html

Supporting docs

• https://discuss.elastic.co/t/upgrading-elastic-agent-via-fleet-in-an-air-gapped-environment-failing/297413
• https://github.com/wise2c-devops/install-elastic-cloud-on-k8s
• [Fleet] Improve support for air-gapped environments without an accessible EPR instance kibana#74614

Discussion points

• External dependencies
• Offline doc ownership
• Breaking changes ownership
• Potential home: Elastic Installation and Upgrade Guide