Topic hierarchy follow up

[cstns]

Description

• restructured hierarchy computed prop to extend functionality
• remember open state for each topic segment
• alter topic count to include deeply nested topics not just immediate children
• add the ability to copy topic path

Related Issue(s)

closes https://github.com/FlowFuse/flowfuse/issues/4801 closes https://github.com/FlowFuse/flowfuse/issues/4802 also implemented a topic open state management mentioned in the main PR as a comment

Checklist

• [x] I have read the contribution guidelines
• [x] Suitable unit/system level tests have been added and they pass
• [ ] Documentation has been updated
  • [ ] Upgrade instructions
  • [ ] Configuration details
  • [ ] Concepts
• [ ] Changes flowforge.yml?
  • [ ] Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • [ ] Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

Labels

• [ ] Includes a DB migration? -> add the area:migration label

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 78.73%. Comparing base (eee84bc) to head (55fb44f). Report is 11 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #4818 +/- ## ======================================= Coverage 78.73% 78.73% ======================================= Files 314 314 Lines 15063 15063 Branches 3461 3461 ======================================= Hits 11860 11860 Misses 3203 3203 ``` | [Flag](https://app.codecov.io/gh/FlowFuse/flowfuse/pull/4818/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FlowFuse) | Coverage Δ | | |---|---|---| | [backend](https://app.codecov.io/gh/FlowFuse/flowfuse/pull/4818/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FlowFuse) | `78.73% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=FlowFuse#carryforward-flags-in-the-pull-request-comment) to find out more.

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