fix: Update legend maxheight calculation logic

[camdecoster]

Description

Update the legend maxheight calculation logic to account for the legend being located above/below the plot. Closes #7473.

Changes

• Updates the maxheight calculation logic
• Moves the default calculation into the sizing method
• Updates attribute description
• Adds test mock for image comparison

Demo

Before	After

Testing instructions

• Be on master
• Create a mock using the config from this PR
• Open the mock in Plotly DevTools
• Note that the legend overlaps the plot
• Switch to this branch
• Open the mock in Plotly DevTools
• Note that the mock shows up correctly

[emilykl]

See comments about the boolean logic and attribute description, otherwise looks good!

[emilykl]

@camdecoster The new image test is failing, can you double check?

[emilykl]

@camdecoster I think the previous version of this docstring correctly reflects what is in the code after your latest changes -- can you confirm?

Suggested change

	'The reference height is the full layout height with the following exceptions: legends to the side of the plot',
	'or vertically oriented legends with a `yref` of `"paper". In this case, the reference height is the plot height.'
	'The reference height is the full layout height, except in the case of vertically oriented legends with',
	'a `yref` of `"paper" located to the side of the plot, in which case the reference height',
	'is the plot height.'

[camdecoster]

As we discussed, you're right. In some JS-like pseudocode:

isAboveBelow = isBelowPlotArea || isAbovePlotArea
!(isAboveBelow || !(orientation === "v" && yref === "paper")) -> !isAboveBelow && !(!(orientation === "v" && yref === "paper")) -> !isAboveBelow && (orientation === "v" && yref === "paper")

I'll switch it back the description back.

For future Cam reference, remember De Morgan's laws.