fix(editor): code block ui issues (#12609)

Close BS-3423
Close BS-3505

<!-- This is an auto-generated comment: release notes by coderabbit.ai -->
## Summary by CodeRabbit

- **Style**
  - Updated toolbar button background color and adjusted layout spacing for toolbar and preview buttons to improve visual consistency.
- **Refactor**
  - Reorganized toolbar menu groups for better clarity, separating toggle and clipboard actions within the code block toolbar.
- **Bug Fixes**
  - Improved UI interaction in code block tests to ensure menus behave as expected without closing prematurely.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/blocks/code/src/code-toolbar/components/code-toolbar.ts

@@ -35,14 +35,10 @@ export class AffineCodeToolbar extends WithDisposable(LitElement) {
 
     .code-toolbar-button {
       color: ${unsafeCSSVarV2('icon/primary')};
-      background-color: ${unsafeCSSVarV2('segment/background')};
+      background-color: ${unsafeCSSVarV2('button/secondary')};
       box-shadow: var(--affine-shadow-1);
       border-radius: 4px;
     }
-
-    .copy-code {
-      margin-left: auto;
-    }
   `;
 
   private _currentOpenMenu: AbortController | null = null;

blocksuite/affine/blocks/code/src/code-toolbar/components/preview-button.ts

@@ -13,6 +13,10 @@ import { CodeBlockPreviewIdentifier } from '../../code-preview-extension';
 
 export class PreviewButton extends WithDisposable(SignalWatcher(LitElement)) {
   static override styles = css`
+    :host {
+      margin-right: auto;
+    }
+
     .preview-toggle-container {
       display: flex;
       padding: 2px;