Performance: Speed up `getHostSibling` for repeating group row generation

[bjosttveit]

Description

React's getHostSibling function can be very slow for renderless components, this will make sure it finds the sibling immediately by adding a HostText fiber-node directly below. The space will be added to the DOM, but should not be visible. See https://github.com/facebook/react/blob/ed15d5007ca7ee4d61294c741ce3e858d3c1d461/packages/react-reconciler/src/ReactFiberCommitHostEffects.js#L222-L226

Edit: Turns out the space will be added to the DOM, but they are at least not visible. I could not find a better or less hacky method of solving this issue.

Related Issue(s)

• https://digdir.slack.com/archives/C076GU2QHCG/p1730812212231269?thread_ts=1730710072.922749&cid=C076GU2QHCG

Verification/QA

• Manual functionality testing
  • [x] I have tested these changes manually
  • [ ] Creator of the original issue (or service owner) has been contacted for manual testing (or will be contacted when released in alpha)
  • [ ] No testing done/necessary
• Automated tests
  • [ ] Unit test(s) have been added/updated
  • [ ] Cypress E2E test(s) have been added/updated
  • [x] No automatic tests are needed here (no functional changes/additions)
  • [ ] I want someone to help me make some tests
• UU/WCAG (follow these guidelines until we have our own)
  • [ ] I have tested with a screen reader/keyboard navigation/automated wcag validator
  • [x] No testing done/necessary (no DOM/visual changes)
  • [ ] I want someone to help me perform accessibility testing
• User documentation @ altinn-studio-docs
  • [ ] Has been added/updated
  • [x] No functionality has been changed/added, so no documentation is needed
  • [ ] I will do that later/have created an issue
• Support in Altinn Studio
  • [ ] Issue(s) created for support in Studio
  • [x] This change/feature does not require any changes to Altinn Studio
• Sprint board
  • [ ] The original issue (or this PR itself) has been added to the Team Apps project and to the current sprint board
  • [ ] I don't have permissions to do that, please help me out
• Labels
  • [x] I have added a kind/* label to this PR for proper release notes grouping
  • [ ] I don't have permissions to add labels, please help me out

[sonarcloud[bot]]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
100.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud