Server side HoverTool follow ups

[hoxbro]

HoloViews:

1. See feat(bokeh): Server side HoverTool for rasterized/datashaded plots with selector #6422 (comment)
   

   holoviews/holoviews/operation/datashader.py

   Lines 1763 to 1766 in 48f91a5

   	# TODO: Investigate why this does not work
   	# element = element.clone(data=new_data, kdims=element.vdims.copy(), vdims=element.vdims.copy())
   	element = element.clone()
   	element.data = new_data

2. Add documentation explaining the difference between selector and aggregator, e.g., that selector is a subset of aggregator, basically that you select a row (min, max, first, last, etc.) and not "combine" multiple rows (mean, std, etc.)

Bokeh (as of Bokeh 3.6, not yet supported in Bokeh)

3. ValueOf(model, attr) needs a configurable formatter bokeh/bokeh#14123
   Currently, we do a simple conversion
4. Provide hit_filter property on HoverTool and TapTool bokeh/bokeh#9087
   Currently, we show the Hovertool even when no data is available, resulting in a HoverTool filled with nans.