build - Refactor Besu custom error prone dependency (#6692)

Move Besu custom error-prone checks into its own repository and use it as an external dependency. This allows to move to a newer version of Google errorprone checks as well while cleaning up build.gradle file.

Key changes resulted due to this change:

* String toLowerCase and toUpperCase to use Locale.ROOT as argument
* Use interface such as List,Map or NavigatableMap instead of concrete class where appropriate.
* Simplify StringBuilder to plain String
* Suppress warnings where appropriate.
-----
Signed-off-by: Usman Saleem <usman@usmans.info>

util/src/main/java/org/hyperledger/besu/util/Subscribers.java

@@ -165,9 +165,7 @@ public class Subscribers<T> {
     }
 
     @Override
-    public void forEach(final Consumer<T> action) {
-      return;
-    }
+    public void forEach(final Consumer<T> action) {}
 
     @Override
     public int getSubscriberCount() {

util/src/test/java/org/hyperledger/besu/util/log/LogUtilTest.java

@@ -114,6 +114,7 @@ public class LogUtilTest {
     return lines;
   }
 
+  @SuppressWarnings("InfiniteRecursion")
   private void recurseTimesAndThrow(final int times) {
     if (times < 1) {
       throw new RuntimeException("FakeStackOverflowError");