[self hosted] Document Gitpod requirement on LoadBalancer type services

[adrienthebo]

Description

At present the Gitpod Kubernetes requirements do not state that Gitpod depends on load balancers that can handle both HTTP(S) and SSH connections. This pull request adds documentation that Gitpod requires layer 4 load balancers and adds links to the appropriate vendor documentation.

Related Issue(s)

Fixes gitpod-io/gitpod#11581

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/cc @MrSimonEmms

This documentation doesn't fully account for the ClusterIP service configuration but we don't appear to have documented this yet; we can either roll in that documentation into this PR or address it shortly after and amend these changes with the updated configs.