chore: avoid repackaging of google elemental dep and use it directly (#12416)

* chore: avoid repackaging of google elemental dep and use it directly

The google elemental dependency is not OSGi compatible so it's repackaged
into shared module to use it directly from there. But there is a custom Vaadin version
of google elemental dep and it's OSGi compatible. Flow uses this version and to be able
to use FW in MPR the versions should match. So the Vaadin google elemental dep is added
instead of repackaging.

* chore: import elemental package in the bnd file

shared/bnd.bnd

@@ -3,7 +3,6 @@ Bundle-Activator: com.vaadin.osgi.resources.OsgiVaadinResources
 Bundle-Name: Vaadin Shared
 Bundle-RequiredExecutionEnvironment: JavaSE-1.8
 Bundle-License: http://www.apache.org/licenses/LICENSE-2.0
-Import-Package: org.osgi*
+Import-Package: org.osgi*, elemental.json*
 Export-Package: com.vaadin.osgi.resources;-noimport:=true,\
-  com.vaadin.shared*;-noimport:=true,\
-  elemental.json*;-noimport:=true
+  com.vaadin.shared*;-noimport:=tru

shared/pom.xml

@@ -33,6 +33,12 @@
             <groupId>org.osgi</groupId>
             <artifactId>osgi.cmpn</artifactId>
         </dependency>
+
+        <dependency>
+            <groupId>com.vaadin.external.gwt</groupId>
+            <artifactId>gwt-elemental</artifactId>
+            <version>2.8.2.vaadin2</version>
+        </dependency>
     </dependencies>
 
     <build>
@@ -51,57 +57,6 @@
                 </executions>
             </plugin>
 
-            <!-- Copy needed GWT dependencies to package -->
-            <plugin>
-                <groupId>org.apache.maven.plugins</groupId>
-                <artifactId>maven-dependency-plugin</artifactId>
-                <executions>
-                    <execution>
-                        <id>unpack-dependencies</id>
-                        <phase>generate-resources</phase>
-                        <goals>
-                            <goal>unpack</goal>
-                        </goals>
-                        <configuration>
-                            <artifactItems>
-                                <artifactItem>
-                                    <groupId>com.google.gwt</groupId>
-                                    <artifactId>gwt-elemental</artifactId>
-                                    <includes>
-                                        elemental/json/**,
-                                        elemental/util/Array*,
-                                        elemental/util/Can*,
-                                        elemental/util/Map*
-                                    </includes>
-                                </artifactItem>
-                            </artifactItems>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
-            <!-- Unpacked Dependencies as source -->
-            <plugin>
-                <groupId>org.codehaus.mojo</groupId>
-                <artifactId>build-helper-maven-plugin</artifactId>
-
-                <!-- Needs extra source folder for unpacked dependencies -->
-                <executions>
-                    <execution>
-                        <id>add-source-path</id>
-                        <phase>generate-sources</phase>
-                        <goals>
-                            <goal>add-source</goal>
-                        </goals>
-                        <configuration>
-                            <sources>
-                                <source>${dependency.unpack.directory}</source>
-                            </sources>
-                        </configuration>
-                    </execution>
-                </executions>
-            </plugin>
-
             <plugin>
                 <artifactId>maven-resources-plugin</artifactId>
                 <executions>