Add 'location.file' to new vulnerability details component

What does this MR do and why?

Adds the finding's file location to the new, GraphQL-only details component. The file is rendered within a separate section "Location", which is also added.

Screenshots or screen recordings

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #371722 (closed)

ee/app/assets/javascripts/security_dashboard/components/shared/vulnerability_details_graphql/index.vue

@@ -92,7 +92,7 @@ export default {
       <p>{{ description }}</p>
     </details-section>
 
-    <details-section>
+    <details-section data-testid="main-section">
       <template #list>
         <details-section-list-item
           :label="$options.i18n.severityLabel"
@@ -115,7 +115,11 @@ export default {
       data-testid="location-section"
     >
       <template #list>
-        <details-section-list-item v-if="location.file" :label="$options.i18n.locationFileLabel">
+        <details-section-list-item
+          v-if="location.file"
+          :label="$options.i18n.locationFileLabel"
+          data-testid="location-file-list-item"
+        >
           <gl-link :href="file.url">{{ file.name }}</gl-link>
         </details-section-list-item>
       </template>