Following VTK, ParaView will be getting deprecation macros instead of relying on
vtkLegacy.h macros that make APIs disappear based on build flags. Instead, users will get warnings upon the use of deprecated APIs which can be suppressed by setting
#define PARAVIEW_DEPRECATION_LEVEL PARAVIEW_VERSION_CHECK(5, 10, 0) to indicate that you need 5.10 compatibility.
Note that APIs deprecated more than a release ago are eligible for removal, so 5.11 may not contain APIs deprecated prior to 5.9 (in fact, the above MR already removes them for 5.11).