ci: run windows CI jobs on PRs (#39139)

Previously windows CI jobs were only run on upstream branches, with the addition
of larger Windows executors as well as the improvement of setup speed in the
windows environment setup script allows for the windows tests to pass in a
reasonable timeframe.

PR Close #39139

.circleci/config.yml

@@ -876,20 +876,12 @@ workflows:
       - test_zonejs:
           requires:
             - setup
-      # Windows Jobs
-      # These are very slow so we run them on non-PRs only for now.
-      # TODO: remove the filter when CircleCI makes Windows FS faster.
-      # The Windows jobs are only run after their non-windows counterparts finish successfully.
-      # This isn't strictly necessary as there is no artifact dependency, but helps economize
-      # CI resources by not attempting to build when we know should fail.
       - test_win:
-          <<: *skip_on_pull_requests
           requires:
-            - test
+            - setup
       - test_ivy_aot_win:
-          <<: *skip_on_pull_requests
           requires:
-            - test_ivy_aot
+            - setup
 
   monitoring:
     jobs:

.circleci/windows-env.ps1

@@ -2,8 +2,8 @@
 # https://docs.bazel.build/versions/master/install-windows.html
 # https://docs.bazel.build/versions/master/windows.html
 # Install MSYS2 and packages
-choco install msys2 --version 20180531.0.0 --no-progress --package-parameters "/NoUpdate"
-C:\tools\msys64\usr\bin\bash.exe -l -c "pacman --needed --noconfirm -S zip unzip patch diffutils git"
+choco install msys2 --version 20200903.0.0 --no-progress --package-parameters "/NoUpdate"
+C:\tools\msys64\usr\bin\bash.exe -l -c "pacman --needed --noconfirm -S zip unzip patch diffutils"
 
 # Add PATH modifications to the Powershell profile. This is the win equivalent of .bash_profile.
 # https://docs.microsoft.com/en-us/previous-versions//bb613488(v=vs.85)