enh: Add Scalebar support for subcoordinate_y plots

[hoxbro]

Resolves #6292

Example:

import holoviews as hv
import numpy as np
hv.extension("bokeh")

common_opts = dict(subcoordinate_y=True, scalebar=True, scalebar_unit=('cm', 'm'),)

c1 = hv.Curve(np.random.rand(1000), label='c1').opts(color='lightblue',  scalebar_location="left", **common_opts)
c2 = hv.Curve(np.random.rand(1000), label='c2').opts(color='indianred', scalebar_location="right", **common_opts)
c3 = hv.Curve(np.random.rand(1000), label='c3').opts(color='plum', scalebar_location="left", **common_opts)
c4 = hv.Curve(np.random.rand(1000), label='c4').opts(color='palegreen', scalebar_location="right", **common_opts)

curves = hv.Overlay(c1 * c2 * c3 * c4).opts(show_legend=False)
curves.opts(width=800, height=600)

[codecov]

Codecov Report

Attention: Patch coverage is 97.29730% with 1 line in your changes missing coverage. Please review.

Project coverage is 88.50%. Comparing base (f9c7f05) to head (65cb860).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
holoviews/plotting/bokeh/element.py	92.85%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6403      +/-   ##
==========================================
+ Coverage   88.48%   88.50%   +0.01%     
==========================================
  Files         323      323              
  Lines       68469    68563      +94     
==========================================
+ Hits        60588    60681      +93     
- Misses       7881     7882       +1     

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[droumis]

@mattpap, is there any way to keep the label text horizontal and put it to the side of a vertically oriented scale bar? Right now, when the text is bigger than the bar, the text will offset the positioning of the bar.

[mattpap]

is there any way to keep the label text horizontal and put it to the side of a vertically oriented scale bar?

Currently label orientation is "idiomatic" and not configurable, but I can add an option for this.

Right now, when the text is bigger than the bar, the text will offset the positioning of the bar.

I suppose that a bug on its own.

[droumis]

Looks good, just with a minor comment/suggestion about getting the renderer.