refactor(editor): split openFileOrFiles into openSingleFileWith and openFilesWith (#12523)

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

- **New Features**
	- Improved file selection dialogs for attachments, imports, and uploads, allowing for more consistent and streamlined file picking across the app.

- **Bug Fixes**
	- Resolved inconsistencies when selecting single or multiple files, ensuring a smoother user experience during file import and upload.

- **Refactor**
	- Unified and simplified file selection logic throughout the app for better reliability and maintainability.
	- Standardized import functions to uniformly handle arrays of files, enhancing consistency in file processing.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

blocksuite/affine/widgets/keyboard-toolbar/src/config.ts

@@ -48,7 +48,7 @@ import { REFERENCE_NODE } from '@blocksuite/affine-shared/consts';
 import type { AffineTextAttributes } from '@blocksuite/affine-shared/types';
 import {
   createDefaultDoc,
-  openFileOrFiles,
+  openSingleFileWith,
   type Signal,
 } from '@blocksuite/affine-shared/utils';
 import type { AffineLinkedDocWidget } from '@blocksuite/affine-widget-linked-doc';
@@ -418,7 +418,7 @@ const contentMediaToolGroup: KeyboardToolPanelGroup = {
         const model = selectedModels?.[0];
         if (!model) return;
 
-        const file = await openFileOrFiles();
+        const file = await openSingleFileWith();
         if (!file) return;
 
         await addSiblingAttachmentBlocks(std, [file], model);
@@ -1040,7 +1040,7 @@ export const defaultKeyboardToolbarConfig: KeyboardToolbarConfig = {
         const model = selectedModels?.[0];
         if (!model) return;
 
-        const file = await openFileOrFiles();
+        const file = await openSingleFileWith();
         if (!file) return;
 
         await addSiblingAttachmentBlocks(std, [file], model);