Experimental: Sparse data

[alxvth]

This PR uses the SparseMatrix implementation from #556 but moves it into an Experimental class to clearly discourage usage since the sparse data API will change.

You may use it right now like this:

auto points = static_cast<Points*>(numericalDataset.getDataset());
size_t numRows = 50;
size_t numCols  = 50;
std::vector<size_t> rowPointers = {};
std::vector<size_t> colIndices = {};
std::vector<float> values = {};

Points::Experimental::setSparseData(points, numRows, numCols, rowPointers, colIndices, values);

events().notifyDatasetDataChanged(numericalDataset);

Additions on top of #556:

• Template row pointer type
• use size_t instead of uint16_t for index type
• use float instead of uint16_t for data type
• Updated setter API in Point data

One usage example is in the HDF5 loader where we currently lock sparse data since no other plugins support it yet.

[ThomasKroes]

This solution seems to work for me on Windows 11. Tried 10 projects with data and they all load without issues.