Refine and restructure Dev Containers docs #5737

Once have the new Dev Containers node, let's explore:

• Creating smaller docs (especially containers.md)
• Restructuring Advanced Containers content
  • Remove or combine any of the topics
  • Bring any important or high-traction topics into main Dev Containers node
  • [Doc] use ${localWorkspaceFolderBasename} in named volume example vscode-remote-release#7444
• Look at stats for above pages and overall content in this node to understand best possible optimizations
• Remove mention of "proposed" or "proposal" from Features descriptions
• Pass over the various aka.ms links for the Dev Containers README, etc
  • Update misleading comment: docker-compose for user devcontainers/templates#65 (comment)
  • https://aka.ms/vscode-remote/containers/non-root to https://aka.ms/dev-containers-non-root
    • Update remoteUser info devcontainers/spec#148
• Move content to spec as possible, i.e. https://github.com/orgs/devcontainers/discussions/4
• Update remote-try-* repos to use latest Template (i.e. Use latest template vscode-remote-try-node#79)
• Update to latest spec info
  • https://code.visualstudio.com/docs/devcontainers/devcontainer-cli is pointing to installing via npm, while I think "open" is only available if you install locally
• Update content based on Dockerfile vs image (https://containers.dev/guide/dockerfile)
  • Learn Module
  • Docs overall