feat: Make SSE endpoint configurable in server transports

This commit updates the WebFluxSseServerTransport, WebMvcSseServerTransport, and HttpServletSseServerTransport classes to accept the SSE endpoint path as a constructor argument.

This change provides more flexibility in configuring the SSE endpoint, allowing it to be customized instead of being hardcoded to "/sse".
It also aligns the Java SDK's behavior with the Python SDK's SseServerTransport, which already supports this customization.

A default SSE endpoint of "/sse" is maintained for backward compatibility.

Also, addressed minor code quality issues identified by SonarLint and reordered modifiers for static final fields to conform with the Java Language Specification.

Signed-off-by: Alexandros Pappas <alexandros.pappas@yiluhub.com>

mcp/src/test/java/org/springframework/ai/mcp/spec/DefaultMcpSessionTests.java

@@ -42,7 +42,7 @@ import static org.assertj.core.api.Assertions.assertThatThrownBy;
  */
 class DefaultMcpSessionTests {
 
-	private final static Logger logger = LoggerFactory.getLogger(DefaultMcpSessionTests.class);
+	private static final Logger logger = LoggerFactory.getLogger(DefaultMcpSessionTests.class);
 
 	private static final Duration TIMEOUT = Duration.ofSeconds(5);