Uploading images through Quick Actions in-place editor fails if the page is edited by multiple users simultaneously

The described behavior is somehow expected given that:

• the image quick action uses the attachments REST resource to upload the image
• the attachments REST resource retrieves the target document by passing failIfLocked=true, see https://github.com/xwiki/xwiki-platform/blob/xwiki-platform-17.5.0/xwiki-platform-core/xwiki-platform-rest/xwiki-platform-rest-server/src/main/java/org/xwiki/rest/internal/resources/attachments/AttachmentsResourceImpl.java#L91
• when failIfLocked=true XWikiResource throws a PRECONDITION_FAILED, see https://github.com/xwiki/xwiki-platform/blob/master/xwiki-platform-core/xwiki-platform-rest/xwiki-platform-rest-server/src/main/java/org/xwiki/rest/XWikiResource.java#L278-L281

When the second user forces the edit lock it gains the lock, which makes the upload fail for the first user because the document is now locked by the second user.

Solved by XWIKI-22163: the quick image upload behaves like an image paste / drop now, so it uses the dedicated CKEditor upload service, which doesn't check if the document is locked.