Add caching to CI jobs (#13712)

- Seems to be improving times for shorter jobs at least.

- Remove Go 1.16.x tests for IAM and replication

.github/workflows/go-cross.yml

@@ -21,9 +21,6 @@ jobs:
         os: [ubuntu-latest]
     steps:
       - uses: actions/checkout@v2
-      - uses: actions/setup-node@v1
-        with:
-          node-version: '12'
       - uses: actions/setup-go@v2
         with:
           go-version: ${{ matrix.go-version }}