Add automated test for "Add a Comment from More Actions Menu"

The manual test is here: Add a Comment from More Actions Menu

Existing automated coverage

• CommentsIT#commentAsLoggedInUser: opens the Comments tab, clicks Comment, adds a comment and asserts it is listed with its author in the Comments section
• CommentsIT#commentAsGuest: same comment posting flow for a guest, from the Comments tab

Missing automated coverage

• On the wiki home page (Main.WebHome), open the More Actions menu and click the "Comments" entry (id tmComment); add a page-object method for it, e.g. via BasePage#clickMoreActionsSubMenuEntry("tmComment")
• Assert the comments viewer is displayed (URL has viewer=comments)
• Click "Comment", type a comment and click "Add Comment"
• Navigate to the home page again and assert the comment is listed in the Comments section at the bottom of the page

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/CommentsIT.java

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