Revert "Build TestPlatform packages in VMR"

[Viktor Hofer (ViktorHofer)]

Reverts #15055

The packages don't build successfully on non-Windows:

  Microsoft.TestPlatform failed with 1 error(s) (0.1s)
    /home/vihofer/git/vstest/.dotnet/sdk/9.0.104/Sdks/NuGet.Build.Tasks.Pack/buildCrossTargeting/NuGet.Build.Tasks.Pack.targets(221,5): error NU5019: File not found: 'net48\Microsoft.TestPlatform.VsTestConsole.TranslationLayer.xml'.
  Microsoft.TestPlatform.Portable failed with 1 error(s) (0.1s)
    /home/vihofer/git/vstest/.dotnet/sdk/9.0.104/Sdks/NuGet.Build.Tasks.Pack/buildCrossTargeting/NuGet.Build.Tasks.Pack.targets(221,5): error NU5019: File not found: 'net48\Microsoft.TestPlatform.VsTestConsole.TranslationLayer.xml'.

I'm a bit suprised that vstest's CI doesn't build packages on non-Windows. Also, the checked-in nuspecs with the hundreds of lines of assets to include are horrible. They made me open this revert PR instead of attempting to fix the build issue.

[Viktor Hofer (ViktorHofer)]

Jakub Jareš (@nohwnd)