[FR]: Support sparse mesh values

[BlueFyre]

Is your feature request related to a problem? Please describe.
The Prusa MK4 mesh will interpolate and extrapolate data when running G29 by default
I would rather visualize the actual probed values rather than this
This can be done by using G29 P1 which skips the other phases but it will leave dots inside the G29 T output

Describe the solution you'd like
It would be nice if the plugin could support sparse data by skipping over those data points

Describe alternatives you've considered
Alternatively, perhaps the plugin could allow setting up which points are actually probed. Though that might be guess work

Additional context
See attached files for sample outputs:
mesh_result_filled.txt
mesh_result_sparse.txt