Resourceadm: refactor about resource form validation + add error summary

[mgunnerud]

Description

• Refactor: move validation out of components and into validation utils function
• Add id to AboutResourcePage components to allow linking directly to fields
• Show ErrorSummary component when there are validation errors in AboutResourcePage
• Add missing validation for resourceReference fields to bff

Related Issue(s)

• 12996

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[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 91.65%. Comparing base (ca477da) to head (1f13f5c). Report is 1 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #12997 +/- ## ========================================== + Coverage 91.63% 91.65% +0.02% ========================================== Files 1410 1410 Lines 19935 19987 +52 Branches 2403 2413 +10 ========================================== + Hits 18267 18320 +53 + Misses 1403 1402 -1 Partials 265 265 ```

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