Authorize feeds in all nuget.config files throughout the repo

tools/Install-NuGetCredProvider.ps1

@@ -46,14 +46,20 @@ if ($IsMacOS -or $IsLinux) {
 if ($AccessToken) {
     $endpoints = @()
 
-    $nugetConfig = [xml](Get-Content -Path "$PSScriptRoot\..\nuget.config")
+    $endpointURIs = @()
+    Get-ChildItem "$PSScriptRoot\..\nuget.config" -Recurse |% {
+        $nugetConfig = [xml](Get-Content -Path $_)
 
-    $nugetConfig.configuration.packageSources.add |? { ($_.value -match '^https://pkgs\.dev\.azure\.com/') -or ($_.value -match '^https://[\w\-]+\.pkgs\.visualstudio\.com/') } |% {
-        $endpoint = New-Object -TypeName PSObject
-        Add-Member -InputObject $endpoint -MemberType NoteProperty -Name endpoint -Value $_.value
-        Add-Member -InputObject $endpoint -MemberType NoteProperty -Name username -Value ado
-        Add-Member -InputObject $endpoint -MemberType NoteProperty -Name password -Value $AccessToken
-        $endpoints += $endpoint
+        $nugetConfig.configuration.packageSources.add |? { ($_.value -match '^https://pkgs\.dev\.azure\.com/') -or ($_.value -match '^https://[\w\-]+\.pkgs\.visualstudio\.com/') } |% {
+            if ($endpointURIs -notcontains $_.Value) {
+                $endpointURIs += $_.Value
+                $endpoint = New-Object -TypeName PSObject
+                Add-Member -InputObject $endpoint -MemberType NoteProperty -Name endpoint -Value $_.value
+                Add-Member -InputObject $endpoint -MemberType NoteProperty -Name username -Value ado
+                Add-Member -InputObject $endpoint -MemberType NoteProperty -Name password -Value $AccessToken
+                $endpoints += $endpoint
+            }
+        }
     }
 
     $auth = New-Object -TypeName PSObject