Use windows-2019 AzDO (hosted) queues

- dotnet/aspnetcore-internal#2538
- stick with BYOC queues for internal builds

nit: remove unused `poolName` parameter

.azure/pipelines/jobs/default-build.yml

@@ -5,8 +5,6 @@
 #       The name of the job. Defaults to the name of the OS. No spaces allowed
 #   jobDisplayName: string
 #       The friendly job name to display in the UI. Defaults to the name of the OS.
-#   poolName: string
-#       The name of the Azure DevOps agent pool to use.
 #   poolVmImage: string
 #       The name of a virtual machine image to use. Primarily of interest when using the Hosted pools.
 #   agentOs: string
@@ -48,7 +46,6 @@
 
 parameters:
   agentOs: 'Windows'
-  poolName: ''
   poolVmImage: ''
   buildArgs: ''
   configuration: 'Release'
@@ -91,17 +88,9 @@ jobs:
       vmImage: macOS-10.13
     ${{ if and(eq(parameters.poolVmImage, ''), eq(parameters.agentOs, 'Linux')) }}:
       vmImage: ubuntu-16.04
-    ${{ if ne(parameters.poolName, '') }}:
-      name: ${{ parameters.poolName }}
-    ${{ if and(eq(parameters.poolName, ''), eq(parameters.agentOs, 'Windows')) }}:
+    ${{ if and(eq(parameters.poolVmImage, ''), eq(parameters.agentOs, 'Windows')) }}:
       ${{ if eq(variables['System.TeamProject'], 'public') }}:
-        name: NetCorePublic-Pool
-        ${{ if ne(parameters.isTestingJob, true) }}:
-          # Visual Studio Build Tools
-          queue: BuildPool.Windows.10.Amd64.VS2019.BT.Open
-        ${{ if eq(parameters.isTestingJob, true) }}:
-          # Visual Studio Enterprise - contains some stuff, like SQL Server and IIS Express, that we use for testing
-          queue: BuildPool.Windows.10.Amd64.VS2019.Open
+        vmImage: windows-2019
       ${{ if eq(variables['System.TeamProject'], 'internal') }}:
         name: NetCoreInternal-Pool
         ${{ if ne(parameters.isTestingJob, true) }}: