Dev container admin docs were scattered across two locations: the Docker-based
integration under extending-templates/ and Envbuilder under managing-templates/.
There was no landing page explaining that two approaches exist or helping admins
choose between them.
This moves everything under admin/integrations/devcontainers/ with a decision
guide at the top. Dev containers are an integration with the dev container
specification, so integrations/ is a natural fit alongside JFrog, Vault, etc.
Stub pages remain at the original locations for discoverability.
New structure:
admin/integrations/devcontainers/
├── index.md # Landing page + decision guide
├── integration.md # Docker-based dev containers
└── envbuilder/
├── index.md
├── add-envbuilder.md
├── envbuilder-security-caching.md
└── envbuilder-releases-known-issues.md
Refs #21080
Mathias Fredriksson