Previously we used a `CellValue` class to hold the data for a cell, and called a function to fill it whenever necessary. This is an unnecessary complication when we have virtual generic arrays and most data is already easily accessible that way anyway. This patch removes `CellValue` and uses `fn::GVArray` to provide access to data instead. In the future, if rows have different types within a single column, we can use a `GVArray` of `blender::Any` to interface with the drawing. Along with that, the use of virtual arrays made it easy to do a few other cleanups: - Use selection domain interpolations from rB5841f8656d95 for the mesh selection filter. - Change the row filter to only calculate for necessary indices. Differential Revision: https://developer.blender.org/D13478