Adding tests for re-instantiation, fixing rare eternal loading

[olemartinorg]

Description

Adding automated tests for re-instantiation. Also removing ref-states and trying to simplify how this works, and making sure to clear an ongoing/failed instantiation when the user leaves the page (such as navigating back to party selection manually) which previously made the app display the loading-spinner indefintely.

Related Issue(s)

• closes App gets stuck on instantiation after switching party #2862
• closes Add automated tests for party selection fix #2997
• tests functionality implemented in Allow instantiation retry after failed attempt #2985

Verification/QA

• Manual functionality testing
  • 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
  • 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
  • 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
  • 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
  • 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
  • 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

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
58.6% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud