feat(richtext-lexical): support copy & pasting and drag & dopping files/images into the editor (#13868)

This PR adds support for inserting images into the rich text editor via
both **copy & paste** and **drag & drop**, whether from local files or
image DOM nodes.

It leverages the bulk uploads UI to provide a smooth workflow for:
- Selecting the target collection
- Filling in any required fields defined on the uploads collection
- Uploading multiple images at once

This significantly improves the UX for adding images to rich text, and
also works seamlessly when pasting images from external editors like
Google Docs or Microsoft Word.

Test pre-release: `3.57.0-internal.801ab5a`

## Showcase - drag & drop images from computer


https://github.com/user-attachments/assets/c558c034-d2e4-40d8-9035-c0681389fb7b

## Showcase - copy & paste images from computer


https://github.com/user-attachments/assets/f36faf94-5274-4151-b141-00aff2b0efa4

## Showcase - copy & paste image DOM nodes


https://github.com/user-attachments/assets/2839ed0f-3f28-4e8d-8b47-01d0cb947edc

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