Update the title to display summary instead of id

Prior to this change, in the vulnerability page, id of the
vulnerability was displayed as title.

This change updates the title to display the human readable
summary for the title, and adds ID as an data decsription.

gcp/appengine/frontend3/src/templates/vulnerability.html

@@ -6,10 +6,12 @@
   <div class="mdc-layout-grid">
     <div class="mdc-layout-grid__inner">
       <div class="mdc-layout-grid__cell--span-12">
-        <h1 class="title">{{ vulnerability.id }}</h1>
+        <h1 class="title">{{ vulnerability.summary }}</h1>
       </div>
       <div class="mdc-layout-grid__cell--span-12">
         <dl class="vulnerability-details">
+          <dt>ID</dt>
+          <dd>{{ vulnerability.id }}</dd>
           {%- if vulnerability.human_source_link -%}
           <dt>Source</dt>
           <dd><a href="{{ vulnerability.human_source_link }}" target="_blank" rel="noopener noreferrer">{{