Performance: add preallocation for some slice/map (#57860)

This change preallocates slices and maps where the size of the data is known before the object is created.

Co-authored-by: Joe Blubaugh <joe.blubaugh@grafana.com>

pkg/services/updatechecker/plugins.go

@@ -146,7 +146,7 @@ func canUpdate(v1, v2 string) bool {
 }
 
 func (s *PluginsService) pluginIDsCSV(m map[string]plugins.PluginDTO) string {
-	var ids []string
+	ids := make([]string, 0, len(m))
 	for pluginID := range m {
 		ids = append(ids, pluginID)
 	}