[Table] Append rows on scroll events

Table should be able to initialize with the rows visible in its viewport and dynamically append rows as the user scrolls down. This will improve its performance on load.

This is a predecessor to virtual-repeat behavior which would create a virtual scrollbar and notify the data source which rows are being viewed for dynamic data loading.

Start from the Table component and its current row initialization and scroll-event handling. Determine how the viewport's visible rows should be identified and how additional rows should be appended; done means the table loads visible rows initially and adds more as the user scrolls down without loading the entire dataset.

Written by the indexing model from the issue text.