Fixes a comment form bug in the diffs app

What does this MR do and why?

This merge request fixes a few bugs within the diffs virtual scroller:

• Fixes a bug the comment form would sometimes randomly scroll the diffs app around. This can be caused by the virtual scroller removing elements from the DOM and then re-adding them causing the mounted autofocus method call to happen when it shouldn't
• Removes a JS error with the ResizeObserver
• Fixes a bug where collapsed files would incorrectly get loaded when scrolling the diffs app
• Fixes a bug where the spacing between diff files would sometimes disappear when scrolling fast

Fixes a comment form bug in the diffs app

This fixes a bug in the diffs virtual scroller where the comment form would get autofocused when the virtual scroller removes and then re-adds the diff file component into the DOM.

Fixes a bug where the virtual scroller would incorrectly load a collapse file on scroll.

Fixes a bug where sometimes the diff files would have no space between them when scrolling fast.

Related Issues:

• #350662 (closed)

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