test: avoid pool pollution in TestSnapshotSlicesAreIndependent

Acquire + Release with RecordMutationEvent / RecordCacheOperationError
leaves the pool holding a collector whose mutationEvents and
cacheOpErrors slices are non-nil empty (NewCacheAnalyticsCollector
leaves them nil; only ResetForReuse'd writes make them non-nil).
Downstream tests that assert.Equal a full CacheAnalyticsSnapshot with
those fields set to nil then pick up the polluted collector and fail.

Use NewCacheAnalyticsCollector directly — the test's purpose is to
prove Snapshot's slice independence, which does not require exercising
the sync.Pool path.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: jensneuse

v2/pkg/engine/resolve/cache_analytics_test.go

@@ -2045,8 +2045,12 @@ func TestSnapshotIndependentOfPooledCollector(t *testing.T) {
 // the snapshot aliases the collector's backing arrays and the next request
 // overwrites positions the caller is still reading.
 func TestSnapshotSlicesAreIndependent(t *testing.T) {
-	c := AcquireCacheAnalyticsCollector()
-	t.Cleanup(func() { ReleaseCacheAnalyticsCollector(c) })
+	// Use a fresh collector instead of Acquire: RecordMutationEvent and
+	// RecordCacheOperationError initialize slices that NewCacheAnalyticsCollector
+	// leaves nil; Releasing the collector would leave the pool with a non-nil
+	// empty slice and break downstream tests that assert.Equal a snapshot with
+	// MutationEvents/CacheOpErrors set to nil.
+	c := NewCacheAnalyticsCollector()
 
 	c.RecordFetchTiming(FetchTimingEvent{DataSource: "ds-orig", DurationMs: 111})
 	c.RecordError(SubgraphErrorEvent{DataSource: "ds-orig"})