use windows-2016 in all builds which compile boringssl (#444)

This change updates the Integration Test and Packaging workflows to use windows-2016 GHA runners.

Details:
GHA is rolling out a new version of windows server 2019 tools (windows-2019 / windows-latest alias) which produce a [C4255 warning](https://docs.microsoft.com/en-us/cpp/error-messages/compiler-warnings/compiler-warning-level-4-c4255?view=msvc-160) in BoringSSL.

BoringSSL is configured to error on all warnings, and so our current CI is broken until we can figure out the best way to properly patch the BoringSSL cmake configuration.

Author: DellaBitta

.github/workflows/cpp-packaging.yml

@@ -246,18 +246,18 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        os: [windows-latest, ubuntu-latest, macos-latest]
+        os: [windows-2016, ubuntu-latest, macos-latest]
         build_type: ["Release", "Debug"]
         architecture: ["x64", "x86"]
         msvc_runtime: ["static", "dynamic"]
         linux_abi: ["legacy", "c++11"]
         python_version: [3.7]
         include:
-        - os: windows-latest
+        - os: windows-2016
           vcpkg_triplet_suffix: "windows-static"
           additional_build_flags: "--build_tests"
           sdk_platform: "windows"
-        - os: windows-latest
+        - os: windows-2016
           msvc_runtime: "dynamic"
           vcpkg_triplet_suffix: "windows-static-md"
           additional_build_flags: "--build_tests"
@@ -272,7 +272,7 @@ jobs:
           sdk_platform: "darwin"
 
         exclude:
-        - os: windows-latest
+        - os: windows-2016
           linux_abi: "c++11"
         - os: macos-latest
           architecture: "x86"

.github/workflows/integration_tests.yml

@@ -18,7 +18,7 @@ on:
         required: true
       operating_systems:
         description: 'CSV of VMs to run on'
-        default: 'ubuntu-latest,windows-latest,macos-latest'
+        default: 'ubuntu-latest,windows-2016,macos-latest'
         required: true
       desktop_ssl_variants:
         description: 'CSV of desktop SSL variants to use'

scripts/gha/print_matrix_configuration.py

@@ -97,7 +97,7 @@
 
   "integration_tests": {
     "matrix": {
-      "os": ["ubuntu-latest", "macos-latest", "windows-latest"],
+      "os": ["ubuntu-latest", "macos-latest", "windows-2016"],
       "platform": ["Desktop", "Android", "iOS"],
       "ssl_lib": ["openssl", "boringssl"],
       "android_device": ["virtual:system-images;android-28;google_apis;x86_64+28.0.3", "real:flame+29"],