github/workflows: Drop VS2017, use preinstalled v142 toolset for VS2019.

The VS 2017 and VS 2019 MSVC CI jobs have been failing intermittently for
months due to Chocolatey/Microsoft installer infrastructure issues when
downloading old Visual Studio build tools onto windows-latest runners.
These are not code failures - the build tools installation itself is
unreliable (CDN timeouts, corrupt downloads, installer self-update loops).

This removes VS 2017 from the matrix entirely and switches VS 2019 to use
the v142 toolset that's already pre-installed on windows-2022 runners as a
component of VS 2022.  The PlatformToolset is now passed explicitly to
MSBuild for both VS 2019 (v142) and VS 2022 (v143), and the Chocolatey
installation step is removed.

VS 2017 reached end-of-life in 2022, and the v141 toolset is no longer
reliably installable on GitHub-hosted runners (actions/runner-images#9701,
actions/runner-images#12764).  The windows-2019 runner image was removed in
June 2025.  Docker containers are not supported on Windows runners, and the
repo's 10GB Actions cache is already full, so caching the installation
isn't feasible either.  MSVC v143 is binary-compatible back to v141, so the
testing value of v141 was marginal.

The net effect is 16 MSVC jobs (down from 24) with zero installation steps
and hopefully no more flaky failures.

Signed-off-by: Andrew Leech <andrew.leech@planetinnovation.com.au>

Author: pi-anl

.github/workflows/ports_windows.yml

@@ -25,23 +25,24 @@ jobs:
         platform: [x86, x64]
         configuration: [Debug, Release]
         variant: [dev, standard]
-        visualstudio: ['2017', '2019', '2022']
+        visualstudio: ['2019', '2022']
         include:
-        - visualstudio: '2017'
-          vs_version: '[15, 16)'
-          custom_vs_install: true
         - visualstudio: '2019'
-          vs_version: '[16, 17)'
-          custom_vs_install: true
+          # The v142 toolset (VS 2019 compiler) is pre-installed on
+          # windows-2022 as a component of VS 2022.  Use VS 2022's
+          # MSBuild and select the v142 toolset via PlatformToolset.
+          vs_version: '[17, 18)'
+          platform_toolset: v142
         - visualstudio: '2022'
           vs_version: '[17, 18)'
+          platform_toolset: v143
         # trim down the number of jobs in the matrix
         exclude:
         - variant: standard
           configuration: Debug
         - visualstudio: '2019'
           configuration: Debug
-    runs-on: windows-latest
+    runs-on: windows-2022
     env:
       CI_BUILD_CONFIGURATION: ${{ matrix.configuration }}
     steps:
@@ -51,31 +52,20 @@ jobs:
       uses: actions/setup-python@v6
       with:
         python-version: '3.11'
-    - name: Install Visual Studio ${{ matrix.visualstudio }}
-      if: matrix.custom_vs_install
-      shell: bash
-      # Shell functions in this block are to retry intermittent corrupt
-      # downloads (with a clean download dir) before failing the job outright
-      run: |
-        try () { ($@) || ($@) || ($@) || ($@) }
-        clean_install () ( rm -rf $TEMP/chocolatey; choco install $1 )
-        try clean_install visualstudio${{ matrix.visualstudio }}buildtools
-        try clean_install visualstudio${{ matrix.visualstudio }}-workload-vctools
-        try clean_install windows-sdk-8.1
     - uses: microsoft/setup-msbuild@v2
       with:
         vs-version: ${{ matrix.vs_version }}
     - uses: actions/checkout@v6
     - name: Build mpy-cross.exe
-      run: msbuild mpy-cross\mpy-cross.vcxproj -maxcpucount -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }}
+      run: msbuild mpy-cross\mpy-cross.vcxproj -maxcpucount -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }} -property:PlatformToolset=${{ matrix.platform_toolset }}
     - name: Update submodules
       run: git submodule update --init lib/micropython-lib
     - name: Build micropython.exe
-      run: msbuild ports\windows\micropython.vcxproj -maxcpucount -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }} -property:PyVariant=${{ matrix.variant }}
+      run: msbuild ports\windows\micropython.vcxproj -maxcpucount -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }} -property:PyVariant=${{ matrix.variant }} -property:PlatformToolset=${{ matrix.platform_toolset }}
     - name: Get micropython.exe path
       id: get_path
       run: |
-        $exePath="$(msbuild ports\windows\micropython.vcxproj -nologo -v:m -t:ShowTargetPath -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }} -property:PyVariant=${{ matrix.variant }})"
+        $exePath="$(msbuild ports\windows\micropython.vcxproj -nologo -v:m -t:ShowTargetPath -property:Configuration=${{ matrix.configuration }} -property:Platform=${{ matrix.platform }} -property:PyVariant=${{ matrix.variant }} -property:PlatformToolset=${{ matrix.platform_toolset }})"
         echo ("micropython=" + $exePath.Trim()) >> $env:GITHUB_OUTPUT
     - name: Run tests
       id: test