[frontend] Relationship display at rel creation from graph (#15575)

[Archidoit]

Proposed changes

When creating a relationship from a container graph, if one of the selected links/nodes is a relationship, display it correctly in the creation form.

Related issues

fixes #15575

[codecov]

Codecov Report

❌ Patch coverage is 27.27273% with 8 lines in your changes missing coverage. Please review.
✅ Project coverage is 33.61%. Comparing base (4df03c8) to head (bf52ea5).
⚠️ Report is 8 commits behind head on master.

Files with missing lines	Patch %	Lines
...ents/graph/components/GraphToolbarContentTools.tsx	0.00%	6 Missing ⚠️
.../opencti-front/src/utils/defaultRepresentatives.ts	60.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #15608      +/-   ##
==========================================
- Coverage   33.62%   33.61%   -0.01%     
==========================================
  Files        3172     3189      +17     
  Lines      214881   217586    +2705     
  Branches    39481    40371     +890     
==========================================
+ Hits        72249    73142     +893     
- Misses     142632   144444    +1812     

Flag	Coverage Δ
opencti-client-python	45.50% <ø> (-0.11%)	⬇️
opencti-front	2.94% <27.27%> (-0.01%)	⬇️
opencti-graphql	70.25% <ø> (+0.29%)	⬆️

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