Alter CI to run Rich Navigation, add new Rich Nav specific pipeline (#22964)

Author: jepetty

Diff for: NuGet.config

@@ -7,6 +7,8 @@
     <add key="dotnet6" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6/nuget/v3/index.json" />
     <add key="dotnet6-transport" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet6-transport/nuget/v3/index.json" />
     <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+    <!-- Used for the Rich Navigation indexing task -->
+    <add key="richnav" value="https://pkgs.dev.azure.com/azure-public/vside/_packaging/vs-buildservices/nuget/v3/index.json" />
   </packageSources>
   <disabledPackageSources />
 </configuration>

Diff for: azure-pipelines-richnav.yml

@@ -0,0 +1,35 @@
+trigger:
+  branches:
+    include:
+      - main
+
+stages:
+- stage: build
+  displayName: Build
+  jobs:
+    - template: eng/common/templates/jobs/jobs.yml
+      parameters:
+        enableMicrobuild: true
+        enableRichCodeNavigation: true
+        richCodeNavigationEnvironment: production
+        helixRepo: dotnet/efcore
+        jobs:
+          - job: Windows
+            timeoutInMinutes: 90
+            enablePublishTestResults: true
+            pool:
+              name: NetCorePublic-Pool
+              queue: BuildPool.Server.Amd64.VS2017.Open
+            steps:
+              - task: NuGetCommand@2
+                displayName: 'Clear NuGet caches'
+                condition: succeeded()
+                inputs:
+                  command: custom
+                  arguments: 'locals all -clear'
+
+              - task: PowerShell@2
+                inputs:
+                  filePath: $(Build.SourcesDirectory)\eng\common\build.ps1
+                  arguments: -restore -build -ci
+                displayName: Build