Move relationship functionality to Turbo Streams

[pixeldesu]

Self-explanatory.

To Do:

• Remove Ajax::RelationshipController and specs
• Remove relationship TypeScript functionality
• Add specs for RelationshipsController

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (0877b93) 95.30% compared to head (e34fda1) 95.34%.

❗ Current head e34fda1 differs from pull request most recent head e802e01. Consider uploading reports for the commit e802e01 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1421      +/-   ##
==========================================
+ Coverage   95.30%   95.34%   +0.04%     
==========================================
  Files         171      171              
  Lines        2682     2666      -16     
==========================================
- Hits         2556     2542      -14     
+ Misses        126      124       -2     

Files	Coverage Δ
app/controllers/relationships_controller.rb	100.00% <100.00%> (ø)

... and 10 files with indirect coverage changes

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