feat: Send multiple files into a single message

[abhipatel0211]

Proposed changes (including videos or screenshots)

Changes

1. Multiple file sharing in one message.
2. Multiple file sharing in one message in E2E encrypted rooms.
3. Functionality of adding and removing files in FileUploadModal.
4. Updated API endpoints rooms.media/:rid and rooms.mediaConfirm/:rid/:fileId to handle multiple files.

Steps to test or reproduce

1. Go to a room.
2. Try sharing multiple files.
3. Confirm file selected.
4. Use the FileUploadModal to add and remove files.

Further comments

This implementation is an initial version of the multiple file sharing feature. While it is functional, some minor bugs remain, particularly with image file sharing, which will be addressed in future updates.

CORE-847

[dougfabris]

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