feat(editor): add collapse/expand functionality to code block component (#14884)

This PR fixes #14040 

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

* **New Features**
* Code blocks can be collapsed and expanded via a toolbar toggle
(visible when the document is editable).
* Collapsed code blocks show a limited preview (~8 lines) with a bottom
fade overlay and reduced padding.
* Toolbar button updates icon and tooltip to reflect collapsed/expanded
state.
* Collapse state is preserved on the block so its current
collapsed/expanded setting is retained.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/components/src/icons/text.ts

@@ -265,6 +265,16 @@ export const CancelWrapIcon = icons.CancelWrapIcon({
   height: '20',
 });
 
+export const CollapseCodeIcon = icons.CollapseIcon({
+  width: '20',
+  height: '20',
+});
+
+export const ExpandCodeIcon = icons.ToggleRightIcon({
+  width: '20',
+  height: '20',
+});
+
 // Attachment
 
 export const ViewIcon = icons.ViewIcon({