Removed designer prefix

[mlqn]

Description

• Removed the /designer prefix from all frontend and backend paths at it does not seem to serve any purpose. 🤷‍♂️
• Removed unused /designerapi and /Home aliases
• Moved frontend files from /wwwroot/designer/frontend/ to /wwwroot/ since wwwroot only contain frontend files

Related Issue(s)

• #{issue number}

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 93.74%. Comparing base (957f1cb) to head (9e33f64).

Additional details and impacted files

@@           Coverage Diff           @@
##             main   #13379   +/-   ##
=======================================
  Coverage   93.74%   93.74%           
=======================================
  Files        1446     1446           
  Lines       20030    20030           
  Branches     2429     2429           
=======================================
  Hits        18778    18778           
  Misses       1004     1004           
  Partials      248      248           

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[mlqn]

I'm closing this PR and converting it to an issue as it's not a priority and it would require more work.
This PR only had a couple of simple commits; the others come from #13254, which has already been merged.