feature symfony#54854 [Stopwatch] Add ROOT constant to make it easier to reference (hacfi)

This PR was merged into the 7.2 branch.

Discussion
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[Stopwatch] Add `ROOT` constant to make it easier to reference

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Issues        | -
| License       | MIT

Just an DX improvement so you can reference the root section with `$stopwatch->getSectionEvents(Stopwatch::ROOT)` instead of `$stopwatch->getSectionEvents('__root__')`.

Commits
-------

fadeafd [Stopwatch] Add `getRootSectionEvents` method `ROOT` constant to `Stopwatch`

Author: fabpot

src/Symfony/Component/Stopwatch/CHANGELOG.md

@@ -5,6 +5,7 @@ CHANGELOG
 ---
 
  * Add method `getLastPeriod()` to `StopwatchEvent`
+ * Add `getRootSectionEvents()` method and `ROOT` constant to `Stopwatch`
 
 5.2
 ---

src/Symfony/Component/Stopwatch/Stopwatch.php

@@ -23,6 +23,8 @@ class_exists(Section::class);
  */
 class Stopwatch implements ResetInterface
 {
+    public const ROOT = '__root__';
+
     /**
      * @var Section[]
      */
@@ -138,14 +140,24 @@ public function getEvent(string $name): StopwatchEvent
      */
     public function getSectionEvents(string $id): array
     {
-        return isset($this->sections[$id]) ? $this->sections[$id]->getEvents() : [];
+        return $this->sections[$id]->getEvents() ?? [];
+    }
+
+    /**
+     * Gets all events for the root section.
+     *
+     * @return StopwatchEvent[]
+     */
+    public function getRootSectionEvents(): array
+    {
+        return $this->sections[self::ROOT]->getEvents() ?? [];
     }
 
     /**
      * Resets the stopwatch to its original state.
      */
     public function reset(): void
     {
-        $this->sections = $this->activeSections = ['__root__' => new Section(null, $this->morePrecision)];
+        $this->sections = $this->activeSections = [self::ROOT => new Section(null, $this->morePrecision)];
     }
 }