refactor: Redesign/refactor next recommended action

[lassopicasso]

Description

This PR updates the user story for component "Tabell for underskjema" based on the latest Figma design for subform and discussions with Anniken.

Design changes:

• Remove the close button below the selector; users must select or create a subform before proceeding.
• Disable autosave when selecting a subform; users must click "Save" to confirm, as re-selection is disabled.
• Restrict relink subform in "Tabell for underskjema" when a subform is already linked.
• When "Create new subform" is clicked, replace the selector with a card containing input-elements, save and slose buttons.
• Keep the user in the current configuration view after creating a new subform (no redirect).
• Replace the warning message with a recommended action card, including instructions and a create-subform card, if no subform layout sets are available.
• Rename the "til utforming" button to "Utform underskjemaet."
• Add an "Utform underskjemaet" button in the open config area below the linked subform.

Code changes:

• Refactor code to support design adjustments.
• Remove outdated text keys for older subform designs.
• Reorganize to be closer to their respective code files and update/remove tests.

Video: Old User Story

gammel-brukerreise-underskjema.mp4

Video: New User Story

ny-brukerreise-underskjema.mp4

Related Issue(s)

• adjust the implementations of Next Recommended Action for Tabell for underskjema #13999

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)
• Relevant automated test added (if you find this hard, leave it and we'll help out)

Documentation

• User documentation is updated with a separate linked PR in altinn-studio-docs. (if applicable)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.30%. Comparing base (4d8c7e3) to head (21d4c71).
Report is 9 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #14032      +/-   ##
==========================================
+ Coverage   95.28%   95.30%   +0.02%     
==========================================
  Files        1763     1762       -1     
  Lines       23000    23005       +5     
  Branches     2676     2677       +1     
==========================================
+ Hits        21915    21926      +11     
+ Misses        836      832       -4     
+ Partials      249      247       -2     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[Jondyr]

Nice refactoring/cleanup of tests👍

[JamalAlabdullah]

Tested ok and works as expected