Change the NuGet feed to use the governed PowerShell feed (#4044)

nuget.config

@@ -2,7 +2,7 @@
 <configuration>
   <packageSources>
     <clear />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+    <add key="PowerShell_PublicPackages" value="https://pkgs.dev.azure.com/powershell/PowerShell/_packaging/powershell/nuget/v3/index.json" />
   </packageSources>
   <disabledPackageSources>
     <clear />

tools/helper.psm1

@@ -339,3 +339,26 @@ function Test-XUnitTestResults
         throw "$($failedTests.failed) tests failed"
     }
 }
+
+<#
+.SYNOPSIS
+    Run 'dotnet restore' for all the target runtime that we are interested in to
+    update packages on the CFS feed.
+    This needs to be run on a MS employee's dev machine whenever there is update
+    to the NuGet packages used in PSReadLine repo, so that the package and all its
+    dependencies can be pull into the CFS feed from upstream feed.
+#>
+function Update-CFSFeed
+{
+    $rids = @('win-x64', 'win-arm64', 'linux-x64', 'linux-arm', 'linux-arm64', 'osx-x64', 'osx-arm64')
+
+    Write-Host "1. clear all NuGet caches on the local machine." -ForegroundColor Green
+    dotnet nuget locals all -c
+
+    Write-Host "2. restore for target runtimes." -ForegroundColor Green
+    foreach ($rid in $rids) {
+        Write-Host "  - $rid" -ForegroundColor Green
+        dotnet restore -r $rid ../test/PSReadLine.Tests.csproj
+        dotnet restore -r $rid ../MockPSConsole/MockPSConsole.csproj
+    }
+}