Skip py.exe launcher tests in full layout CI test (GH-100948)

These tests become flaky when py.exe exists on the test machine but isn't the one that was just built. They also don't provide any useful information for this scenario, so easiest to just skip them.
(cherry picked from commit 5ff029f)

Co-authored-by: Steve Dower <[email protected]>

Author: miss-islington

.azure-pipelines/windows-layout-steps.yml

@@ -12,7 +12,7 @@ steps:
   displayName: Show layout info (${{ parameters.kind }})
 
 - ${{ if eq(parameters.fulltest, 'true') }}:
-  - script: .\python.exe -m test -q -uall -u-cpu -rwW --slowest --timeout=1200 -j0 --junit-xml="$(Build.BinariesDirectory)\test-results-${{ parameters.kind }}.xml" --tempdir "$(Build.BinariesDirectory)\tmp-${{ parameters.kind }}-$(arch)"
+  - script: .\python.exe -m test -q -uall -u-cpu -rwW --slowest --timeout=1200 -j0 --junit-xml="$(Build.BinariesDirectory)\test-results-${{ parameters.kind }}.xml" --tempdir "$(Build.BinariesDirectory)\tmp-${{ parameters.kind }}-$(arch)" -i test_launcher
     workingDirectory: $(Build.BinariesDirectory)\layout-${{ parameters.kind }}-$(arch)
     displayName: ${{ parameters.kind }} Tests
     env: