Run ASAN and TSAN on both macOS and ubuntu (#10310)

Author: dconeybe

.github/workflows/firestore.yml

@@ -126,14 +126,15 @@ jobs:
   sanitizers:
     # Don't run on private repo unless it is a PR.
     if: (github.repository == 'Firebase/firebase-ios-sdk' && github.event_name == 'schedule') || github.event_name == 'pull_request'
-    # TODO(b/231154868): GRPC 1.44 cause link issues on Mac, moving it to Ubuntu for now and add Mac when it is resolved.
-    runs-on: ubuntu-latest
     needs: check
 
     strategy:
       matrix:
+        os: [macos-12, ubuntu-latest]
         sanitizer: [asan, tsan]
 
+    runs-on: ${{ matrix.os }}
+
     env:
       SANITIZERS: ${{ matrix.sanitizer }}