legend not working for bar plot with Plotly backend

I would expect the `legend` attribute to also work for the Plotly backend in the example below. But it does not.


```python
import hvplot.pandas # noqa

from bokeh.sampledata.autompg import autompg_clean as df

table = df.groupby('yr').mean(numeric_only=True)
table.head()

table = df.groupby(['yr', 'origin']).mean(numeric_only=True)
table.head()

hvplot.extension("bokeh")
table.hvplot.bar(stacked=True, height=500, legend='bottom')

hvplot.extension("plotly")
table.hvplot.bar(stacked=True, height=500, legend='bottom')
```

## HoloViews

I've tried to replicate this using HoloViews. But it seems the corresponding `legend_position` is only supported for the `matplotlib` and `bokeh` backends. There is an existing FR in HoloViews to support `legend_position` for the Plotly backend. See https://github.com/holoviz/holoviews/issues/5221

It is possible to position the Plotly legend using a hook though.

```python
import holoviews as hv # noqa

hv.extension("plotly")

from bokeh.sampledata.autompg import autompg_clean as df

table = df.groupby(['yr', 'origin']).mean(numeric_only=True)

def hook(plot, element):
# https://plotly.com/python/legend/#legend-positioning
fig = plot.state
fig["layout"]["legend"]=dict(
yanchor="top",
y=0.99,
xanchor="left",
x=0.01
)

plot = hv.Bars(table, kdims=["yr", "origin"], vdims="mpg").opts(stacked=True, height=500, width=1000, hooks=[hook])

import panel as pn

pn.extension()

pn.panel(plot).servable()
```


## Additional Context

I've been working on improving the `bar` docs. As a part of this I try changing the plotting backend. I would really, really like the documentation to work for all plotting backends. That is what I would expect as a user.