Backport of ci: Run `go mod tidy` check on submodules into release/1.15.x (#19746)

backport of commit 5316676bb6

Co-authored-by: Michael Zalimeni <michael.zalimeni@hashicorp.com>

.github/workflows/reusable-check-go-mod.yml

@@ -26,7 +26,8 @@ jobs:
     - uses: actions/setup-go@6edd4406fa81c3da01a34fa6f6343087c207a568 # pin@v3.5.0
       with:
         go-version-file: 'go.mod'
-    - run: go mod tidy
+    # Run on all go.mod (include submodules).
+    - run: make go-mod-tidy
     - run: |
         if [[ -n $(git status -s) ]]; then
           echo "Git directory has changes"