THRIFT-5568: enforce consistent Java formatting (#2581)

* use spotless plugin and google-java-format to enforce a consistent code format
* add a step of spotless check before building
* only run spotless on the src/ directory

Co-authored-by: Christopher Tubbs <ctubbsii@apache.org>
diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 227b6ce..f82e8a4 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -77,6 +77,11 @@
           sudo ln -s /usr/local/gradle/bin/gradle /usr/local/bin
           gradle --version
 
+      - name: Run spotlessCheck
+        run: |
+          cd lib/java
+          gradle spotlessCheck
+
       - name: Run bootstrap
         run: ./bootstrap.sh