Update search_query callback

[ole-alb]

Update png2mesh to match the changed search_query callback from t8code, which was updated in:
split search_query callback function into two
and
Changed return type of query function to void

[holke]

Great changes, thank you!

Did you test the code?

I think this now raises the dependency on t8code to 3.0.0? Then we should add that in the CMake file

[ole-alb]

I tested it by running the demo and by executing it with different pngs.

Yeah we should add t8code 3.0.0 as soon as we made the release.