Fix some issues caught by IntelliJ static code analysis

The most common issues were:
* Arrays.asList() shouldn't be called with a single parameter.
* Broken Javadoc @links.
* Unnecessary casts and type declarations.
* Unnecessary unused variable initializations.

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=230994311

java/google/registry/keyring/api/ComparatorKeyring.java

@@ -181,7 +181,7 @@ public final class ComparatorKeyring extends ComparingInvocationHandler<Keyring>
       return "null";
     }
 
-    StringBuilder builder = new StringBuilder("");
+    StringBuilder builder = new StringBuilder();
     for (byte b : a.getFingerprint()) {
       builder.append(String.format("%02x:", b));
     }