More tweaks for the tree reporter TUI

[godlygeek]

• Use a gradient for rows in the table, rather than just 4 color buckets by size
• Hide the location and thread labels for the root node, since they don't apply to it
• Show 200 allocation locations in the tree by default, rather than the previous default of 10
• Add a node to the tree showing information about the allocations other than the 200 that made the cut. Selecting it gives information about how to rerun the reporter to include more of them.
• Update the tests to reflect these changes