plot_cells_3d() display colData values when hovering over cells

[Sgonzal97]

When calling plot_cells_3d() and coloring the umap by the expression of a gene of interest, it would be nice to know more about what cells are expressing that gene. Currently, this requires calling plot_cells_3d() again, but coloring the cells by cell type (or timepoint, cluster, etc), and re-orienting yourself in the plotly window to find the cells from your previous window.

In addition, hovering over a cell reveals "trace 0" if that cell is expressing the gene of interest, or "trace 1" if it is not. This doesn't give us any new information that we can't already see.

I think that plot_cells_3d() would be more intuitive if hovering over a cell displayed that cell's value for a colData col of our choice - coloring cells by gene expression, but hovering reveals a timepoint value, or a cell type, or cluster value, or drug treatment, etc.