Should categorical rasterized plots have a colorbar by default?

[maximlt]

At the moment, these types of plots have a colorbar by default, as that's the default for all rasterized plots. I don't find the greyscale colorbar to be very useful (I'd rather have a nice legend by default ;) holoviz/holoviews#6638).

import hvplot.pandas  # noqa
import hvsampledata
import datashader as ds

df = hvsampledata.synthetic_clusters("pandas")

plot_opts = dict(x='x', y='y', data_aspect=1, frame_height=250)
df.hvplot.points(
    rasterize=True, aggregator=ds.by('cat'),
    title="Categorical rasterizing with\n'count' aggregator'", **plot_opts
)