Scale up the following IGV GUI elements on high-DPI displays (e.g. 4K resolution):

- default zoom level (too small)
- filter view (font scales but not the line height)
- buttons above the graph view and outline (too small)
- splash screen (too small)

Original report by [~neliasso]: https://github.com/openjdk/jdk/pull/3361#pullrequestreview-629743706

The attached screenshot (also by [~neliasso]) illustrates some of the scaling issues on a 4K display.