feat(editor): show doc title in page block (#9975)

Close [BS-2392](https://linear.app/affine-design/issue/BS-2392/page-block-需要显示文章title)

### What Changes
- Add `<doc-title>` to edgeless page block (a.k.a the first page visible note block)
- Refactors:
  - Move `<doc-title>` to `@blocksuite/affine-component`, but you can aslo import it from `@blocksuite/preset`
  - Extract `<edgeless-note-mask>` and `<edgeless-note-background>` from `<affine-edgeless-note>` to a seperate file
  - Rewrite styles of `<affine-edgeless-note>` with `@vanilla-extract/css`

https://github.com/user-attachments/assets/a0c03239-803e-4bfa-b30e-33b919213b12

blocksuite/affine/shared/src/services/feature-flag-service.ts

@@ -18,7 +18,7 @@ export interface BlockSuiteFlags {
   enable_shape_shadow_blur: boolean;
   enable_mobile_keyboard_toolbar: boolean;
   enable_mobile_linked_doc_menu: boolean;
-  enable_page_block_header: boolean;
+  enable_page_block: boolean;
 }
 
 export class FeatureFlagService extends StoreExtension {
@@ -41,7 +41,7 @@ export class FeatureFlagService extends StoreExtension {
     enable_shape_shadow_blur: false,
     enable_mobile_keyboard_toolbar: false,
     enable_mobile_linked_doc_menu: false,
-    enable_page_block_header: false,
+    enable_page_block: false,
   });
 
   setFlag(key: keyof BlockSuiteFlags, value: boolean) {