feat(subform): texts to inform user invalid subform layout

[Jondyr]

Description

• Added a new hook to validate a subform layout.
• Used SubFormMissingContentWarning from feat(subform): Add SubFormMissingContentWarning Component #13813 to show a warning if validation is not passed

Related Issue(s)

• Texts to inform user that they must configure subform layoutset before they can configure TableHeaders, with link to subForm layoutset #13682

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 (51ce6ed) to head (c62ce68).
Report is 1 commits behind head on 10-17-add_subformmissingcontentwarning_component.

Additional details and impacted files

@@                                Coverage Diff                                @@
##           10-17-add_subformmissingcontentwarning_component   #13834   +/-   ##
=================================================================================
  Coverage                                             95.30%   95.30%           
=================================================================================
  Files                                                  1650     1651    +1     
  Lines                                                 21975    21991   +16     
  Branches                                               2581     2583    +2     
=================================================================================
+ Hits                                                  20943    20959   +16     
  Misses                                                  787      787           
  Partials                                                245      245           

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[JamalAlabdullah]

Nice work 🙂 I just commented a small things,
and also wonder if we can add a space between the header and the warning message.

[JamalAlabdullah]

Veldig bra 😊