Remove configure layoutsets panel and adapt css on layoutsets dropdown

[standeren]

Description

• Delete configure layout sets panel as this convertion is provided through the upgrade script.

• Remove the check for existing layoutsets in LayoutSetsContainer in v4 since all v4 apps will have the layoutsets file anyway.

• Adapt css on layout sets container native select in order to be consistent in width undependant of the contnet in the select.

• #{issue number}

Verification

• Your code builds clean without any errors or warnings
• Manual testing done (required)

[codecov]

Codecov Report

Attention: Patch coverage is 80.00000% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 88.10%. Comparing base (1163fa7) to head (609c9d8).

Files	Patch %	Lines
.../ux-editor-v3/src/components/Elements/Elements.tsx	75.00%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #12472      +/-   ##
==========================================
+ Coverage   87.52%   88.10%   +0.57%     
==========================================
  Files        1274     1271       -3     
  Lines       18489    18321     -168     
  Branches     2294     2263      -31     
==========================================
- Hits        16183    16141      -42     
+ Misses       2032     1910     -122     
+ Partials      274      270       -4     

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[lassopicasso]

Well done! 🚀