fix(editor): loading style (#12537)

Closes: [BS-3555](https://linear.app/affine-design/issue/BS-3555/ui-attachment-loading-变量更新)
Closes: [BS-3559](https://linear.app/affine-design/issue/BS-3559/ui-图片-loading-变量更新)

### Dark
<img width="625" alt="Screenshot 2025-05-26 at 20 32 36" src="https://github.com/user-attachments/assets/93501e3d-8fc6-45f9-84a0-ac147e5c5f9f" />

### Light
<img width="623" alt="Screenshot 2025-05-26 at 20 32 25" src="https://github.com/user-attachments/assets/7d5bc128-6667-45b5-982d-dab3a22706a7" />

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

- **New Features**
  - Loading icons are now invoked as functions, allowing for more flexible and customizable rendering with parameters like size and progress.

- **Refactor**
  - Replaced theme-dependent and static loading icon references with a unified `LoadingIcon()` component across multiple components and blocks.
  - Removed legacy icon variants and simplified icon import statements, centralizing icon rendering logic.

- **Style**
  - Updated styles for loading and reload buttons to use theme-aware CSS variables.
  - Enlarged and repositioned loading indicators in image blocks for better visibility.

- **Bug Fixes**
  - Achieved consistent loading icon rendering across various blocks and components by standardizing icon invocation.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/blocks/embed-doc/src/embed-synced-doc-block/styles.ts

@@ -303,11 +303,11 @@ export const cardStyles = css`
     align-items: center;
     gap: 4px;
     cursor: pointer;
+    color: ${unsafeCSSVarV2('button/primary')};
   }
   .affine-embed-synced-doc-card-content-reload-button svg {
     width: 12px;
     height: 12px;
-    fill: var(--affine-background-primary-color);
   }
   .affine-embed-synced-doc-card-content-reload-button > span {
     display: -webkit-box;
@@ -317,7 +317,6 @@ export const cardStyles = css`
     white-space: normal;
     overflow: hidden;
     text-overflow: ellipsis;
-    color: var(--affine-brand-color);
     font-family: var(--affine-font-family);
     font-size: var(--affine-font-xs);
     font-style: normal;