Fix cannot apply both size and shape to points in a plot-by series

[jnumainville]

Fixes #3323

Verified by running the code from the issue above:

from deephaven import empty_table
from deephaven.plot import Figure
import math

math_funcs = ["sin", "cos"]
shapes = ["SQUARE", "CIRCLE", "UP_TRIANGLE", "DOWN_TRIANGLE", "RIGHT_TRIANGLE", "LEFT_TRIANGLE", "DIAMOND"]
size = 50
# Unsupported shapes: ["ELLIPSE", "HORIZONTAL_RECTANGLE", "VERTICAL_RECTANGLE"]

# Create a generic table that has enough columns to display all the shapes
# Re-uses some of the funcs
t = empty_table(size).update([f"name=`` + shapes[(int)Math.floor(i / Math.ceil(size / {len(shapes)}))]", "x=i*0.1"])
for i in range(len(shapes)):
    t = t.update([f"y{i}=Math.{math_funcs[i % len(math_funcs)]}(x+{math.floor(i / len(math_funcs))})"])

# Create a plot by figure
p2 = Figure().plot_xy(series_name="Multi", t=t, by=["name"], x="x", y="y1").line(visible=True)
for i in range(len(shapes)):
    # apply both shapes and sizes to points
    p2 = p2.point(shape=shapes[i], multi_series_key=[shapes[i]], size=len(shapes) - i, visible=True)
p2 = p2.show()

With the following graph as an output:

The different series have different shapes and sizes, as expected.

[github-actions]

CLA Assistant Lite bot All contributors have signed the CLA ✍️ ✅

[jnumainville]

I have read the CLA Document and I hereby sign the CLA

[jmao-denver]

The change does make the code a little harder to follow but I don't see a clearly better alternative.