[WIP] [SPARK-3996]: Shade Jetty in Spark deliverables

This patch piggy-back's on @vanzin's work to simplify the Guava shading,
and adds Jetty as a shaded library in Spark. Other than adding Jetty,
it consilidates the <artifactSet>'s into the root pom. I found it was
a bit easier to follow that way, since you don't need to look into
child pom's to find out specific artifact sets included in shading.

network/common/pom.xml

@@ -101,18 +101,6 @@
           </execution>
         </executions>
       </plugin>
-      <plugin>
-        <groupId>org.apache.maven.plugins</groupId>
-        <artifactId>maven-shade-plugin</artifactId>
-        <configuration>
-          <shadedArtifactAttached>false</shadedArtifactAttached>
-          <artifactSet>
-            <includes>
-              <include>com.google.guava:guava</include>
-            </includes>
-          </artifactSet>
-        </configuration>
-      </plugin>
     </plugins>
   </build>
 </project>

pom.xml

@@ -1276,10 +1276,26 @@
           <shadedArtifactAttached>false</shadedArtifactAttached>
           <artifactSet>
             <includes>
+              <!-- At a minimum we must include this to force effective pom generation -->
               <include>org.spark-project.spark:unused</include>
+
+              <include>org.eclipse.jetty:jetty-io</include>
+              <include>org.eclipse.jetty:jetty-http</include>
+              <include>org.eclipse.jetty:jetty-plus</include>
+              <include>org.eclipse.jetty:jetty-security</include>
+              <include>org.eclipse.jetty:jetty-util</include>
+              <include>org.eclipse.jetty:jetty-server</include>
+              <include>com.google.guava:guava</include>
             </includes>
           </artifactSet>
           <relocations>
+            <relocation>
+              <pattern>org.eclipse.jetty</pattern>
+              <shadedPattern>org.spark-project.jetty</shadedPattern>
+              <includes>
+                <include>org.eclipse.jetty.**</include>
+              </includes>
+            </relocation>
             <relocation>
               <pattern>com.google.common</pattern>
               <shadedPattern>org.spark-project.guava</shadedPattern>