Make toString(), hashCode(), equals() and friends final in AutoValue classes

Developers usually don't look at the classes that AutoValue generates,
but at the hand-written classes. If the hand-written classes implement
toString(), hashCode(), equals() etc, AutoValue doesn't override them.
To make this more clear to readers of the hand-written classes
ErrorProne suggests to make these methods final.

See https://errorprone.info/bugpattern/AutoValueFinalMethods

Enable this check at ERROR severity to prevent future occurrences.

Signed-off-by: Edwin Kempin <ekempin@google.com>
Change-Id: I972e8e8f9339b811c78157abef771b8c32be079c

java/com/google/gerrit/server/config/ConfigKey.java

@@ -34,7 +34,7 @@ public abstract class ConfigKey {
   }
 
   @Override
-  public String toString() {
+  public final String toString() {
     StringBuilder sb = new StringBuilder();
     sb.append(section()).append(".");
     if (subsection() != null) {

java/com/google/gerrit/server/config/ScheduleConfig.java

@@ -194,7 +194,7 @@ public abstract class ScheduleConfig {
   }
 
   @Override
-  public String toString() {
+  public final String toString() {
     StringBuilder b = new StringBuilder();
     b.append(formatValue(keyInterval()));
     b.append(", ");