relayer arranger view and extract button_2 and button_3 to top level

plugin/vst/src/cache.rs

@@ -0,0 +1,19 @@
+use std::sync::Arc;
+
+use crate::{editor::Editor, prelude::*};
+
+pub(crate) struct PluginCache {
+    pub info: Info,
+    pub params: Arc<dyn PluginParameters>,
+    pub editor: Option<Box<dyn Editor>>,
+}
+
+impl PluginCache {
+    pub fn new(info: &Info, params: Arc<dyn PluginParameters>, editor: Option<Box<dyn Editor>>) -> Self {
+        Self {
+            info: info.clone(),
+            params,
+            editor,
+        }
+    }
+}