Refactor timeline event list

What does this MR do and why?

Describe in detail what your merge request does and why.

In order to allow that addition of edit functionality in timeline events as in #344060 (closed), the timeline event list must be refactored so that app/assets/javascripts/issues/show/components/incidents/timeline_events_form.vue can be used within the list.

No visual changes, only refactoring

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How to set up and validate locally

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

MR acceptance checklist

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

app/assets/javascripts/issues/show/components/incidents/timeline_events_item.vue

@@ -50,39 +50,43 @@ export default {
 };
 </script>
 <template>
-  <div class="gl-display-flex gl-align-items-center">
-    <div
-      class="gl-display-flex gl-align-items-center gl-justify-content-center gl-bg-white gl-text-gray-200 gl-border-gray-100 gl-border-1 gl-border-solid gl-rounded-full gl-mt-n2 gl-mr-3 gl-w-8 gl-h-8 gl-p-3 gl-z-index-1"
-    >
-      <gl-icon :name="getEventIcon(action)" class="note-icon" />
-    </div>
-    <div
-      class="timeline-event-note gl-w-full gl-display-flex gl-flex-direction-row"
-      :class="{ 'gl-pb-3 gl-border-gray-50 gl-border-1 gl-border-b-solid': !isLastItem }"
-      data-testid="event-text-container"
-    >
-      <div>
-        <strong class="gl-font-lg" data-testid="event-time">
-          <gl-sprintf :message="$options.i18n.timeUTC">
-            <template #time>{{ time }}</template>
-          </gl-sprintf>
-        </strong>
-        <div v-safe-html="noteHtml"></div>
+  <li
+    class="timeline-entry timeline-entry-vertical-line note system-note note-wrapper gl-my-2! gl-pr-0!"
+  >
+    <div class="gl-display-flex gl-align-items-center">
+      <div
+        class="gl-display-flex gl-align-items-center gl-justify-content-center gl-bg-white gl-text-gray-200 gl-border-gray-100 gl-border-1 gl-border-solid gl-rounded-full gl-mt-n2 gl-mr-3 gl-w-8 gl-h-8 gl-p-3 gl-z-index-1"
+      >
+        <gl-icon :name="getEventIcon(action)" class="note-icon" />
       </div>
-      <gl-dropdown
-        v-if="canUpdate"
-        right
-        class="event-note-actions gl-ml-auto gl-align-self-center"
-        icon="ellipsis_v"
-        text-sr-only
-        :text="$options.i18n.moreActions"
-        category="tertiary"
-        no-caret
+      <div
+        class="timeline-event-note gl-w-full gl-display-flex gl-flex-direction-row"
+        :class="{ 'gl-pb-3 gl-border-gray-50 gl-border-1 gl-border-b-solid': !isLastItem }"
+        data-testid="event-text-container"
       >
-        <gl-dropdown-item @click="$emit('delete')">
-          {{ $options.i18n.delete }}
-        </gl-dropdown-item>
-      </gl-dropdown>
+        <div>
+          <strong class="gl-font-lg" data-testid="event-time">
+            <gl-sprintf :message="$options.i18n.timeUTC">
+              <template #time>{{ time }}</template>
+            </gl-sprintf>
+          </strong>
+          <div v-safe-html="noteHtml"></div>
+        </div>
+        <gl-dropdown
+          v-if="canUpdate"
+          right
+          class="event-note-actions gl-ml-auto gl-align-self-center"
+          icon="ellipsis_v"
+          text-sr-only
+          :text="$options.i18n.moreActions"
+          category="tertiary"
+          no-caret
+        >
+          <gl-dropdown-item @click="$emit('delete')">
+            <gl-button>{{ $options.i18n.delete }}</gl-button>
+          </gl-dropdown-item>
+        </gl-dropdown>
+      </div>
     </div>
-  </div>
+  </li>
 </template>