build: move main and setup to SLNX (#43478)

Closes #37100

This does not migrate the rest of the solutions (why do we have so
many?)

Not migrated:

- TemplateCmdPalExtension.sln
- FancyZonesEditor.sln
- BugReportTool.sln
- CleanUp_tool.sln
- FancyZones_DrawLayoutTest.sln
- FancyZones_zonable_tester.sln
- FancyZone_HitTest.sln
- MonitorReportTool.sln
- PowerToyTemplate.sln
- StylesReportTool.sln

---------

Co-authored-by: vanzue <vanzue@outlook.com>

.pipelines/v2/templates/job-build-project.yml

@@ -192,14 +192,14 @@ jobs:
     displayName: Verify XAML formatting
 
   - pwsh: |-
-      & '.pipelines/verifyNugetPackages.ps1' -solution '$(build.sourcesdirectory)\PowerToys.sln'
-    displayName: Verify Nuget package versions for PowerToys.sln
+      & '.pipelines/verifyNugetPackages.ps1' -solution '$(build.sourcesdirectory)\PowerToys.slnx'
+    displayName: Verify Nuget package versions for PowerToys.slnx
 
   - pwsh: |-
-      & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\PowerToys.sln'
+      & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\PowerToys.slnx'
       & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\tools\BugReportTool\BugReportTool.sln'
       & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\tools\StylesReportTool\StylesReportTool.sln'
-      & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\installer\PowerToysSetup.sln'
+      & '.pipelines/verifyArm64Configuration.ps1' -solution '$(build.sourcesdirectory)\installer\PowerToysSetup.slnx'
     displayName: Verify ARM64 configurations
 
   - ${{ if eq(parameters.enablePackageCaching, true) }}:
@@ -252,7 +252,7 @@ jobs:
     ${{ else }}:
       displayName: Build PowerToys main project
     inputs:
-      solution: 'PowerToys.sln'
+      solution: 'PowerToys.slnx'
       vsVersion: 17.0
       msbuildArgs: >-
         -restore -graph
@@ -275,7 +275,7 @@ jobs:
     displayName: Generate DSC artifacts for ARM64
     condition: and(succeeded(), eq(variables['BuildPlatform'], 'arm64'))
     inputs:
-      solution: PowerToys.sln
+      solution: PowerToys.slnx
       vsVersion: 17.0
       msbuildArgs: >-
         -restore

.pipelines/v2/templates/job-build-ui-tests.yml

@@ -74,7 +74,7 @@ jobs:
       command: restore
       feedsToUse: config
       configPath: nuget.config
-      restoreSolution: PowerToys.sln
+      restoreSolution: PowerToys.slnx
       restoreDirectory: '$(Build.SourcesDirectory)\packages'
 
   # Build all UI test projects if no specific modules are specified
@@ -129,4 +129,4 @@ jobs:
   - publish: $(JobOutputDirectory)
     artifact: $(JobOutputArtifactName)
     displayName: Publish UI Test artifacts
-    condition: always()
+    condition: always()

.pipelines/v2/templates/steps-build-installer-vnext.yml

@@ -35,7 +35,7 @@ steps:
   - task: VSBuild@1
     displayName: Build Shared Support DLLs
     inputs:
-      solution: "**/installer/PowerToysSetup.sln"
+      solution: "**/installer/PowerToysSetup.slnx"
       vsVersion: 17.0
       msbuildArgs: >-
         /t:PowerToysSetupCustomActionsVNext;SilentFilesInUseBAFunction
@@ -74,7 +74,7 @@ steps:
   - task: VSBuild@1
     displayName: 💻 Build VNext MSI
     inputs:
-      solution: "**/installer/PowerToysSetup.sln"
+      solution: "**/installer/PowerToysSetup.slnx"
       vsVersion: 17.0
       msbuildArgs: >-
         -restore
@@ -91,7 +91,7 @@ steps:
   - task: VSBuild@1
     displayName: 👤 Build VNext MSI
     inputs:
-      solution: "**/installer/PowerToysSetup.sln"
+      solution: "**/installer/PowerToysSetup.slnx"
       vsVersion: 17.0
       msbuildArgs: >-
         /t:PowerToysInstallerVNext
@@ -142,7 +142,7 @@ steps:
   - task: VSBuild@1
     displayName: 💻 Build VNext Bootstrapper
     inputs:
-      solution: "**/installer/PowerToysSetup.sln"
+      solution: "**/installer/PowerToysSetup.slnx"
       vsVersion: 17.0
       msbuildArgs: >-
         -restore
@@ -159,7 +159,7 @@ steps:
   - task: VSBuild@1
     displayName: 👤 Build VNext Bootstrapper
     inputs:
-      solution: "**/installer/PowerToysSetup.sln"
+      solution: "**/installer/PowerToysSetup.slnx"
       vsVersion: 17.0
       msbuildArgs: >-
         /t:PowerToysBootstrapperVNext

.pipelines/v2/templates/steps-update-winappsdk-and-restore-nuget.yml

@@ -54,4 +54,13 @@ steps:
     feedsToUse: 'config'
     nugetConfigPath: '$(build.sourcesdirectory)\nuget.config'
     restoreSolution: '$(build.sourcesdirectory)\**\*.sln'
-    includeNuGetOrg: false
+    includeNuGetOrg: false
+
+- task: NuGetCommand@2
+  displayName: 'Restore NuGet packages (slnx)'
+  inputs:
+    command: 'restore'
+    feedsToUse: 'config'
+    nugetConfigPath: '$(build.sourcesdirectory)\nuget.config'
+    restoreSolution: '$(build.sourcesdirectory)\**\*.slnx'
+    includeNuGetOrg: false