Fix various Error Prone errors that were found by the FOSS build

Most common:
- Unnecessary parentheses and operator precedence clarify (self-explanatory)
- Reference equality--there were a few instances of using == or != improperly
- Qualification of Builder (and similar) imports so that it's clear which type of Builder we're referring to
- Marking some immutable classes with @Immutable since EP desires that all enums be deeply immutable
- String.split() having "surprising behavior"

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=230971531

java/google/registry/util/CidrAddressBlock.java

@@ -450,7 +450,7 @@ public class CidrAddressBlock implements Iterable<InetAddress>, Serializable {
         }
 
         InetAddress next = InetAddresses.increment(previous);
-        return (contains(next)) ? next : null;
+        return contains(next) ? next : null;
       }
     };
   }

java/google/registry/util/DiffUtils.java

@@ -138,7 +138,7 @@ public final class DiffUtils {
           && ((DiffPair) value).b instanceof Set) {
         DiffPair pair = ((DiffPair) value);
         String prettyLineDiff = prettyPrintSetDiff((Set<?>) pair.a, (Set<?>) pair.b) + "\n";
-        output = newPath + ((prettyLineDiff.startsWith("\n")) ? ":" : ": ") + prettyLineDiff;
+        output = newPath + (prettyLineDiff.startsWith("\n") ? ":" : ": ") + prettyLineDiff;
       } else {
         output = newPath + ": " + value + "\n";
       }

java/google/registry/util/PosixTarHeader.java

@@ -279,9 +279,9 @@ public final class PosixTarHeader {
   @Override
   public boolean equals(@Nullable Object rhs) {
     return rhs == this
-        || rhs != null
-        && getClass() == rhs.getClass()
-        && Arrays.equals(header, ((PosixTarHeader) rhs).header);
+        || (rhs != null
+            && getClass() == rhs.getClass()
+            && Arrays.equals(header, ((PosixTarHeader) rhs).header));
   }
 
   /** @see Arrays#toString(byte[]) */

java/google/registry/util/XmlEnumUtils.java

@@ -21,7 +21,11 @@ public class XmlEnumUtils {
   /** Read the {@link XmlEnumValue} string off of an enum. */
   public static String enumToXml(Enum<?> input) {
     try {
-      return input.getClass().getField(input.name()).getAnnotation(XmlEnumValue.class).value();
+      return input
+          .getDeclaringClass()
+          .getField(input.name())
+          .getAnnotation(XmlEnumValue.class)
+          .value();
     } catch (NoSuchFieldException e) {
       throw new RuntimeException(e);
     }