fix: only show Cell Selection drag handle w/using mixed/cell selection

[ghiscoding]

we shouldn't show the Cell Selection drag handle, unless we are using the new Hybrid Selection Model ("mixed" or "cell", but not "row"), it's also unusable unless we are in the hybrid mode, so no reason to show it if it ain't usable

[6pac]

Noting that the cell selection feature (ie. visible handle) should be available under either the cell selection or hybrid selection model. The hybrid selection model was introduced in the same PR as drag-fill, but they are not related. Really, the cell drag handle should be visible in either the cell selection model, or when the hybrid selection model is in cell selection mode. Perhaps we need a default setting to enable/disable drag-select.

[ghiscoding]

Noting that the cell selection feature (ie. visible handle) should be available under either the cell selection or hybrid selection model. The hybrid selection model was introduced in the same PR as drag-fill, but they are not related. Really, the cell drag handle should be visible in either the cell selection model, or when the hybrid selection model is in cell selection mode. Perhaps we need a default setting to enable/disable drag-select.

feel free to review that or improve it, but per some basic tests I've done, it really shouldn't appear at all when using Row Selection which was the main fix in this PR. Also I don't think that it works with the regular SlickCellSelectionModel, so I removed it for that one too

[6pac]

OK, all good