Update copyright headers to 2025 and clean up code

- Add copyright headers to files missing them
- Add blank lines after copyright headers for consistency
- Remove unused imports in test files
- Remove unnecessary keep-alive warning logs in WebFlux and WebMvc transport providers

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

mcp-test/src/main/java/io/modelcontextprotocol/AbstractMcpClientServerIntegrationTests.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2024 - 2024 the original author or authors.
  */
+
 package io.modelcontextprotocol;
 
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;

mcp-test/src/main/java/io/modelcontextprotocol/AbstractStatelessIntegrationTests.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2024 - 2024 the original author or authors.
  */
+
 package io.modelcontextprotocol;
 
 import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;

mcp-test/src/main/java/io/modelcontextprotocol/client/AbstractMcpAsyncClientResiliencyTests.java

@@ -1,6 +1,7 @@
 /*
  * Copyright 2024-2024 the original author or authors.
  */
+
 package io.modelcontextprotocol.client;
 
 import eu.rekawek.toxiproxy.Proxy;

mcp-test/src/main/java/io/modelcontextprotocol/server/TestUtil.java

@@ -1,6 +1,7 @@
 /*
 * Copyright 2025 - 2025 the original author or authors.
 */
+
 package io.modelcontextprotocol.server;
 
 import java.io.IOException;