Style container's label as unnamed

[abey79]

What

This PR styles the container label like unnamed space views in the blueprint tree and the children list (container selection panel). It also fixes the UI and behaviour of tiles tabs for container (which typically appear when a tab container's direct child is also a container).

• Fixes Style containers in the same way as unnamed space view #4966

Checklist

• I have read and agree to Contributor Guide and the Code of Conduct
• I've included a screenshot or gif (if applicable)
• I have tested the web demo (if applicable):
  • Using newly built examples: app.rerun.io
  • Using examples from latest main build: app.rerun.io
  • Using full set of examples from nightly build: app.rerun.io
• The PR title and labels are set such as to maximize their usefulness for the next release's CHANGELOG

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