Remove old debug UI

[VillePihlava]

Summary

This PR removes the old debug UI (application/src/client/classic-debug). I also removed and changed some related documentation.

Issue

N/A

Unit tests

N/A

Documentation

I changed doc/user/Troubleshooting-Routing.md and doc/user/Frontends.md to indicate of this change. I did a quick search for more references of the old debug UI but could not find any. However, there might still be some references left in the documentation.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 70.10%. Comparing base (a7c5aec) to head (da4d1ef).
Report is 46 commits behind head on dev-2.x.

Additional details and impacted files

@@            Coverage Diff             @@
##             dev-2.x    #6478   +/-   ##
==========================================
  Coverage      70.10%   70.10%           
+ Complexity     18269    18267    -2     
==========================================
  Files           2077     2077           
  Lines          77659    77659           
  Branches        7828     7828           
==========================================
  Hits           54439    54439           
- Misses         20439    20440    +1     
+ Partials        2781     2780    -1     

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[leonardehrenfried]

You're also deleting the new debug UI and GraphiQL. Both of those we want to keep. :)

Deleting classic-debug is enough.

[VillePihlava]

You're also deleting the new debug UI and GraphiQL. Both of those we want to keep. :)

Deleting classic-debug is enough.

My mistake, thanks for pointing this out :D

[optionsome]

I converted this to draft since I was informed there still exist some debug layer related instructions for some OSM editors in Finland that haven't been yet updated to be about the new debug UI. Hopefully soon we can get rid of this.