## Issue
Closes 6159 "Support Comments Enabled/Disabled for comment.List API"
## New behavior
- `disable-comments` tag will block the comments component entirely.
- `settings.commentsEnabled`:
- When false, will pause comment fetching, posting and replying.
- Any already-fetched comments will stay on screen (unless user reloads/F5).
(1) Reduced the debouncing duration so that the final element can be rendered asap after visible.
- If the user is scrolling non-stop, it would continue to debounce and the GUI ends up not showing the final element.
- 25ms seems enough to prevent the initial false-positive that occurs in the scenario of "adjacent/upper elements resized late, so our element was briefly on screen when mounted". If not enough, we can make this a parameter.
(2) Removed `lastUpdateDate` that was a quick hack for Recommended section. We don't use it on that element anymore, so remove the hack to keep the file clean.
(1) The previous code assumed the element is always smaller than the screen. When used on large items like "homepage categories", it'll never load because the element exceeds the screen width or height.
(2) Added optional placeholder element. This allows us to put a cheaper element while waiting, so that the layout doesn't shift when we finally render. This is visually better when scrolling, and complies with Web Vitals.
