Pipeline console improvements

[timja]

Changes:

• Collapsible tree view
• View step log link
• Steps that don't log much no longer take up lots of room when expanded
• Split pane's initial size ratio adjusted so that log area is larger
• Custom styling removed for resizer, it seems fine without it
• 'bubble's around stages removed so only active stage has a 'bubble'

Other changes I would like to do:

• Change it so there's only one scroll bar for the log area instead of per step, the per step one is clunky and poor UX from my experience but I haven't managed to get this working.
• A 'fly-out' for a step so you can 'full-screen' the logs

Testing done

Submitter checklist

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4. Link to relevant issues in GitHub or Jira
5. Link to relevant pull requests, esp. upstream and downstream changes
6. Ensure you have provided tests - that demonstrates feature works or fixes the issue