Pre-install & xharness adb devices

Now `pwsh integration-test/android.Tests.ps1` device/emulator discovery
works without adb in PATH or ANDROID_SERIAL explicitly defined.

Author: jpnurmi

integration-test/android.Tests.ps1

@@ -8,16 +8,14 @@ BeforeDiscovery {
     # Skip Android integration tests unless an emulator has been already started
     # by Android Device Tests, or manually when testing locally. This avoids
     # slowing down non-Device Test CI builds further.
+    Install-XHarness
     $script:emulator = Get-AndroidEmulatorId
 }
 
 Describe 'MAUI app' -ForEach @(
     @{ tfm = "net9.0-android35.0" }
 ) -Skip:(-not $script:emulator) {
     BeforeAll {
-        . $PSScriptRoot/../scripts/device-test-utils.ps1
-        Install-XHarness
-
         Remove-Item -Path "$PSScriptRoot/mobile-app" -Recurse -Force -ErrorAction SilentlyContinue
         Copy-Item -Path "$PSScriptRoot/net9-maui" -Destination "$PSScriptRoot/mobile-app" -Recurse -Force
         Push-Location $PSScriptRoot/mobile-app

scripts/device-test-utils.ps1

@@ -16,7 +16,7 @@ function Get-AndroidEmulatorId {
     }
     try
     {
-        return & adb devices | Select-String "device$" | ForEach-Object { ($_ -split "`t")[0] } | Select-Object -First 1
+        return & xharness android adb -- devices | Select-String "device$" | ForEach-Object { ($_ -split "`t")[0] } | Select-Object -First 1
     }
     catch
     {