Add automated test for "Attach Same File Twice"

The manual test is here: Attach Same File Twice

Existing automated coverage

• AttachmentIT#uploadAttachments: uploads from the Attachments tab, clicks Hide upload status, re-uploads a file with the same name and asserts the latest version becomes 1.2 and its link serves the new content
• DownloadAttachmentRevisionIT#downloadRevision: two uploads of the same file name; revisions 1.1 and 1.2 are both downloadable with their own content
• MoveAttachmentIT#moveAttachment: after two uploads of the same file name and a move, clicks the version link in the Attachments pane and asserts the history page lists 1.1 and 1.2 with size, author and content (no date)

Missing automated coverage

• Upload a file from the Attachments tab, click "Hide upload status", upload the same file again
• Click the "1.2" version link (AttachmentsPane#goToAttachmentHistory) without any move
• Assert the history lists versions 1.1 and 1.2, each with its size, author and date (add an AttachmentHistoryPage getter for the date column)

Suggested location: xwiki-platform-core/xwiki-platform-flamingo/xwiki-platform-flamingo-skin/xwiki-platform-flamingo-skin-test/xwiki-platform-flamingo-skin-test-docker/src/test/it/org/xwiki/flamingo/test/docker/AttachmentIT.java

Found by comparing the XWiki 18.4.4 manual test runs against the automated tests on master (a0055f10a1a).