Switch references to master to main in the codebase + validating infra post-main migration (#44347)

* Update package.json

* Remove references to master in the codebase

* Add more master - main

.github/workflows/ci.yml

@@ -3,11 +3,11 @@ name: CI
 on:
   push:
     branches:
-      - master
+      - main
       - release-*
   pull_request:
     branches:
-      - master
+      - main
       - release-*
 
 jobs:

.github/workflows/sync-branch.yaml

@@ -28,8 +28,8 @@ jobs:
     - run: |
         git config user.email "typescriptbot@microsoft.com"
         git config user.name "TypeScript Bot"
-        git fetch origin master
-        git merge origin/master --no-ff
+        git fetch origin main
+        git merge origin/main --no-ff
         npm ci
         npm test
         git push