`plot_callback_raster_multiday` / `plot_callback_raster_multiblock`: sort by arbitrarily many time parameters

[cirorandazzo]

Workaround fix for block/timepoint ordering in this commit is kinda janky (sort by timepoint + 0.01 * block).

What would be ideal is this: refactor plot_callback_raster_multiday & plot_callback_raster_multiblock into a single function (maybe plot_callback_raster_timepoints, which can take in a tuple of several levels & plots according to this order. Maybe pass in different dicts for each timepoint line styling + a list of bools for whether to plot secondary axes (can you even plot multiple secondary axes on the same side of the plot? maybe plot just the first by default).

[cirorandazzo]

Related: I believe legend entries currently populate from only the final "block" (term used loosely) to be added. Refactoring should fix this as well.

For example, this plot only has stim in the legends since the final block contains no calls.