Introduce factory methods in SslInfo and remove MockSslInfo

After further consideration, we have decided to remove the recently
introduced MockSslInfo in favor of introducing the following static
factory methods directly in the SslInfo interface.

- SslInfo.from(String sessionId)

- SslInfo from(String sessionId, X509Certificate... peerCertificates)

See gh-35042
See gh-35078

spring-test/src/test/java/org/springframework/test/web/reactive/server/samples/bind/ApplicationContextTests.java

@@ -24,7 +24,7 @@ import org.springframework.context.ApplicationContext;
 import org.springframework.context.annotation.Configuration;
 import org.springframework.context.annotation.Import;
 import org.springframework.http.server.reactive.ServerHttpRequest;
-import org.springframework.mock.http.server.reactive.MockSslInfo;
+import org.springframework.http.server.reactive.SslInfo;
 import org.springframework.test.context.junit.jupiter.SpringJUnitConfig;
 import org.springframework.test.web.reactive.server.WebTestClient;
 import org.springframework.web.bind.annotation.GetMapping;
@@ -65,7 +65,7 @@ class ApplicationContextTests {
 	@Test  // gh-35042
 	void buildWithSslInfo() {
 		var client = WebTestClient.bindToApplicationContext(context)
-				.sslInfo(new MockSslInfo("test123"))
+				.sslInfo(SslInfo.from("test123"))
 				.webFilter(new SslSessionIdFilter())
 				.build();