[BE][CI] Add windows test run instructions (#90388)

Specifies how to activate VisualStudio, Anaconda and set `PYTHONPATH` to run tests in CI
Pull Request resolved: https://github.com/pytorch/pytorch/pull/90388
Approved by: https://github.com/atalman, https://github.com/ZainRizvi

.github/workflows/_win-build.yml

@@ -56,7 +56,7 @@ jobs:
             And then change password using `passwd` command.
 
             To start build locally, change working folder to \actions-runner\_work\pytorch\pytorch,
-            Activate miniconda and Visual Studio environment, but running:
+            Activate miniconda and Visual Studio environment, by running:
               call C:\Jenkins\Miniconda3\Scripts\activate.bat C:\Jenkins\Miniconda3
               call "C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Auxiliary\Build\vcvarsall.bat" x64
 

.github/workflows/_win-test.yml

@@ -78,6 +78,16 @@ jobs:
         uses: pytorch/test-infra/.github/actions/setup-ssh@main
         with:
           github-secret: ${{ secrets.GITHUB_TOKEN }}
+          instructions: |
+            To forward remote desktop on your local machine ssh as follows:
+              ssh -L 3389:localhost:3389 %%username%%@%%hostname%%
+            And then change password using `passwd` command.
+
+            To start tests locally, change working folder to \actions-runner\_work\pytorch\pytorch\test,
+            Activate miniconda and Visual Studio environment and set PYTHON_PATH, by running:
+              call C:\Jenkins\Miniconda3\Scripts\activate.bat C:\Jenkins\Miniconda3
+              call "C:\Program Files (x86)\Microsoft Visual Studio\2019\BuildTools\VC\Auxiliary\Build\vcvarsall.bat" x64
+              set PYTHONPATH=C:\actions-runner\_work\pytorch\pytorch\build\win_tmp\build
 
       - name: Start monitoring script
         id: monitor-script