add intellij metadata for the plugin and packages templates (#11852)

packages/flutter_tools/templates/package/.idea/libraries/Dart_SDK.xml.tmpl

+<component name="libraryTable">
+  <library name="Dart SDK">
+    <CLASSES>
+      <root url="file://{{dartSdk}}/lib/async" />
+      <root url="file://{{dartSdk}}/lib/collection" />
+      <root url="file://{{dartSdk}}/lib/convert" />
+      <root url="file://{{dartSdk}}/lib/core" />
+      <root url="file://{{dartSdk}}/lib/developer" />
+      <root url="file://{{dartSdk}}/lib/html" />
+      <root url="file://{{dartSdk}}/lib/indexed_db" />
+      <root url="file://{{dartSdk}}/lib/io" />
+      <root url="file://{{dartSdk}}/lib/isolate" />
+      <root url="file://{{dartSdk}}/lib/js" />
+      <root url="file://{{dartSdk}}/lib/js_util" />
+      <root url="file://{{dartSdk}}/lib/math" />
+      <root url="file://{{dartSdk}}/lib/mirrors" />
+      <root url="file://{{dartSdk}}/lib/svg" />
+      <root url="file://{{dartSdk}}/lib/typed_data" />
+      <root url="file://{{dartSdk}}/lib/web_audio" />
+      <root url="file://{{dartSdk}}/lib/web_gl" />
+      <root url="file://{{dartSdk}}/lib/web_sql" />
+    </CLASSES>
+    <SOURCES />
+  </library>
+</component>
\ No newline at end of file

packages/flutter_tools/templates/package/.idea/modules.xml.tmpl

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="ProjectModuleManager">
+    <modules>
+      <module fileurl="file://$PROJECT_DIR$/{{projectName}}.iml" filepath="$PROJECT_DIR$/{{projectName}}.iml" />
+      <module fileurl="file://$PROJECT_DIR$/{{projectName}}_android.iml" filepath="$PROJECT_DIR$/{{projectName}}_android.iml" />
+    </modules>
+  </component>
+</project>

packages/flutter_tools/templates/package/.idea/workspace.xml.tmpl

+<?xml version="1.0" encoding="UTF-8"?>
+<project version="4">
+  <component name="FileEditorManager">
+    <leaf>
+      <file leaf-file-name="main.dart" pinned="false" current-in-tab="true">
+        <entry file="file://$PROJECT_DIR$/lib/main.dart">
+          <provider selected="true" editor-type-id="text-editor">
+            <state relative-caret-position="0">
+              <caret line="0" column="0" lean-forward="false" selection-start-line="0" selection-start-column="0" selection-end-line="0" selection-end-column="0" />
+            </state>
+          </provider>
+        </entry>
+      </file>
+    </leaf>
+  </component>
+  <component name="ToolWindowManager">
+    <editor active="true" />
+    <layout>
+      <window_info id="Project" active="false" anchor="left" auto_hide="false" internal_type="DOCKED" type="DOCKED" visible="true" show_stripe_button="true" weight="0.25" sideWeight="0.5" order="0" side_tool="false" content_ui="combo" />
+    </layout>
+  </component>
+  <component name="ProjectView">
+    <panes>
+      <pane id="ProjectPane">
+        <option name="show-excluded-files" value="false" />
+      </pane>
+    </panes>
+  </component>
+</project>