Bring codebase up to more recent Java standards (#2422)

This includes using the new switch format (though IntelliJ does not yet
understand patterns including default so those aren't used), multiline strings,
replacing some unnecessary type declarations with <>, converting some classes to
records, replacing some Guava predicates with native Java code, and some other
miscellaneous Code Inspection fixes.

proxy/src/main/java/google/registry/proxy/GcpJsonFormatter.java

@@ -98,30 +98,15 @@ class GcpJsonFormatter extends Formatter {
    *     href="https://github.com/googleapis/google-cloud-java/blob/master/google-cloud-clients/google-cloud-logging/src/main/java/com/google/cloud/logging/LoggingHandler.java#L325">{@code LoggingHandler}</a>
    */
   private static String severityFor(Level level) {
-    switch (level.intValue()) {
-        // FINEST
-      case 300:
-        return "DEBUG";
-        // FINER
-      case 400:
-        return "DEBUG";
-        // FINE
-      case 500:
-        return "DEBUG";
-        // CONFIG
-      case 700:
-        return "INFO";
-        // INFO
-      case 800:
-        return "INFO";
-        // WARNING
-      case 900:
-        return "WARNING";
-        // SEVERE
-      case 1000:
-        return "ERROR";
-      default:
-        return "DEFAULT";
-    }
+    return switch (level.intValue()) {
+      case 300 -> "DEBUG"; // FINEST
+      case 400 -> "DEBUG"; // FINER
+      case 500 -> "DEBUG"; // FINE
+      case 700 -> "INFO"; // CONFIG
+      case 800 -> "INFO"; // INFO
+      case 900 -> "WARNING"; // WARNING
+      case 1000 -> "ERROR"; // SEVERE
+      default -> "DEFAULT";
+    };
   }
 }

proxy/src/test/java/google/registry/proxy/EppProtocolModuleTest.java

@@ -48,10 +48,12 @@ class EppProtocolModuleTest extends ProtocolModuleTest {
   private static final String CLIENT_ADDRESS = "epp.client.tld";
 
   private static final byte[] HELLO_BYTES =
-      ("<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n"
-              + "<epp xmlns=\"urn:ietf:params:xml:ns:epp-1.0\">\n"
-              + "  <hello/>\n"
-              + "</epp>\n")
+      """
+          <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+          <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+            <hello/>
+          </epp>
+          """
           .getBytes(UTF_8);
 
   private X509Certificate certificate;

proxy/src/test/java/google/registry/proxy/handler/EppServiceHandlerTest.java

@@ -53,10 +53,12 @@ import org.junit.jupiter.api.Test;
 class EppServiceHandlerTest {
 
   private static final String HELLO =
-      "<?xml version=\"1.0\" encoding=\"UTF-8\" standalone=\"no\"?>\n"
-          + "<epp xmlns=\"urn:ietf:params:xml:ns:epp-1.0\">\n"
-          + "  <hello/>\n"
-          + "</epp>\n";
+      """
+          <?xml version="1.0" encoding="UTF-8" standalone="no"?>
+          <epp xmlns="urn:ietf:params:xml:ns:epp-1.0">
+            <hello/>
+          </epp>
+          """;
 
   private static final String RELAY_HOST = "registry.example.tld";
   private static final String RELAY_PATH = "/epp";