mesh bp utils, paint nestsets

[cyrush]

pull in code this code from Ascent so we can use it more widely (VisIt)

https://github.com/Alpine-DAV/ascent/blob/f9253d49848e3f520d1c9fadcacb68f149c2441c/src/ascent/runtimes/ascent_main_runtime.cpp#L1852

This code paints a ghost field that reflects AMR nesting info