Use Node v14 in Windows CircleCI jobs

Summary:
CircleCI's Windows executor currently ships with a pre-LTS release of Node v12, breaking our Windows jobs ([example](https://app.circleci.com/pipelines/github/facebook/react-native/9280/workflows/21e6e59c-d853-47a1-af62-1368c8ce10ce/jobs/203983)) following facebook#30637, ultimately due to jestjs/jest#10685 dropping support for non-LTS versions in the Node v12 release line.

Luckily, the Windows executor [does ship with nvm](circleci/circleci-docs#3733) so we can use that to install a desired Node version. Rather than just pinning a later v12 release that is LTS, we align the Windows config with the one for non-Windows jobs (in the `nodelts` executor) by running against the latest available Node v14 release.

Changelog:
[Internal]

Differential Revision: D28896581

fbshipit-source-id: bd9dd3eb1921f7ab28f05088db23a54cf1a6478d

.circleci/config.yml

@@ -27,6 +27,7 @@ executors:
   nodelts:
     <<: *defaults
     docker:
+      # Note: Version set separately for Windows builds, see below.
       - image: circleci/node:14
   nodeprevlts:
     <<: *defaults
@@ -618,12 +619,17 @@ jobs:
       - ANDROID_HOME: "C:\\Android\\android-sdk"
       - ANDROID_NDK: "C:\\Android\\android-sdk\\ndk\\20.1.5948944"
       - ANDROID_BUILD_VERSION: 30
-      - ANDROID_TOOLS_VERSION: 30.0.2
+      - ANDROID_TOOLS_VERSION: 29.0.3
       - GRADLE_OPTS: -Dorg.gradle.daemon=false
       - NDK_VERSION: 20.1.5948944
     steps:
       - checkout
 
+      - run
+          name: Install Node
+          # Note: Version set separately for non-Windows builds, see above.
+          command: nvm install 14 && nvm use 14
+
       # Setup Dependencies
       - run:
           name: Install Yarn