test(plugins): speed up integration tests (~45% improvement) (#5137)

* test(plugins): speed up integration tests with shared wazero cache

Reduce plugin test suite runtime from ~22s to ~12s by:

- Creating a shared wazero compilation cache directory in TestPlugins()
  and setting conf.Server.CacheFolder globally so all test Manager
  instances reuse compiled WASM binaries from disk cache
- Moving 6 createTestManager* calls from inside It blocks to BeforeAll
  blocks in scrobbler_adapter_test.go and manager_call_test.go
- Replacing time.Sleep(2s) in KVStore TTL test with Eventually polling
- Reducing WebSocket callback sleeps from 100ms to 10ms

Signed-off-by: Deluan <deluan@navidrome.org>

* test(plugins): enhance websocket tests by storing server messages for verification

Signed-off-by: Deluan <deluan@navidrome.org>

---------

Signed-off-by: Deluan <deluan@navidrome.org>

plugins/plugins_suite_test.go

@@ -36,6 +36,20 @@ var (
 func TestPlugins(t *testing.T) {
 	tests.Init(t, false)
 	buildTestPlugins(t, testDataDir)
+
+	// Create a shared wazero compilation cache directory.
+	// All test managers will point CacheFolder here so that WASM compilation
+	// is done once per binary and then reused from disk cache.
+	sharedCacheDir, err := os.MkdirTemp("", "plugins-shared-cache-*")
+	if err != nil {
+		t.Fatalf("Failed to create shared cache dir: %v", err)
+	}
+	t.Cleanup(func() { os.RemoveAll(sharedCacheDir) })
+
+	// Set CacheFolder globally so all tests (including those using
+	// configtest.SetupConfig) inherit it without needing to set it manually.
+	conf.Server.CacheFolder = sharedCacheDir
+
 	log.SetLevel(log.LevelFatal)
 	RegisterFailHandler(Fail)
 	RunSpecs(t, "Plugins Suite")
@@ -114,7 +128,6 @@ func createTestManagerWithPluginsAndMetrics(pluginConfig map[string]map[string]s
 	conf.Server.Plugins.Enabled = true
 	conf.Server.Plugins.Folder = tmpDir
 	conf.Server.Plugins.AutoReload = false
-	conf.Server.CacheFolder = filepath.Join(tmpDir, "cache")
 
 	// Setup mock DataStore with pre-enabled plugins
 	mockPluginRepo := tests.CreateMockPluginRepo()