[JENKINS-72028] replace deprecated URL() at core/src/main/java/hudson/ (#8565)

* missing 'alt' attribute added

* missing 'alt' attribute added

* replaced 'new URL' to 'new URI' per Java 11 target codebase

* Revert "replaced 'new URL' to 'new URI' per Java 11 target codebase"

This reverts commit aeef4c1e4b.

* replaced deprecated URL() with URI#.toURL()

* updated code per review

* updated

* updated code

* added back file

* Update core/src/main/java/hudson/cli/InstallPluginCommand.java

Co-authored-by: James Nord <jtnord@users.noreply.github.com>

* Update core/src/main/java/hudson/TcpSlaveAgentListener.java

remove non required as per suggestion

Co-authored-by: James Nord <jtnord@users.noreply.github.com>

* Update core/src/main/java/hudson/model/UpdateSite.java

Co-authored-by: James Nord <jtnord@users.noreply.github.com>

* Update core/src/main/java/hudson/model/UpdateSite.java

* Spotless

---------

Co-authored-by: Alexander Brandes <mc.cache@web.de>
Co-authored-by: James Nord <jtnord@users.noreply.github.com>

core/src/main/java/hudson/Functions.java

@@ -110,7 +110,6 @@ import java.lang.reflect.Type;
 import java.net.MalformedURLException;
 import java.net.URI;
 import java.net.URISyntaxException;
-import java.net.URL;
 import java.net.URLDecoder;
 import java.net.URLEncoder;
 import java.nio.charset.StandardCharsets;
@@ -1939,11 +1938,11 @@ public class Functions {
         String url = Jenkins.get().getRootUrl();
         try {
             if (url != null) {
-                String host = new URL(url).getHost();
+                String host = new URI(url).toURL().getHost();
                 if (host != null)
                     return host;
             }
-        } catch (MalformedURLException e) {
+        } catch (MalformedURLException | URISyntaxException e) {
             // fall back to HTTP request
         }
         return Stapler.getCurrentRequest().getServerName();