Refactor SQL agent and related nodes

- Rename `VectorStoreAgent` to `Vector store agent` in `custom.py`
- Replace "Construct a sql agent from an LLM and tools." with "Construct an SQL agent from an LLM and tools." in `custom.py`
- Update descriptions of `SQLAgentNode`, `TimeTravelGuideChainNode`, `CombineDocsChainNode`, and `ToolNode` in related files
- Increase width of `ExtraSidebarComponent` container in `index.tsx` from 52 to 56

src/frontend/src/pages/FlowPage/components/extraSidebarComponent/index.tsx

@@ -72,7 +72,7 @@ export default function ExtraSidebar() {
   }
 
   return (
-    <div className="w-52 flex flex-col overflow-hidden scrollbar-hide h-full border-r">
+    <div className="w-56 flex flex-col overflow-hidden scrollbar-hide h-full border-r">
       <div className="mt-2 mb-2 w-full flex gap-2 justify-between px-2 items-center">
         <ShadTooltip delayDuration={1000} content="Import" side="top">
           <button