ENH: add cline to Styler.to_latex

[attack68]

• closes ENH: Styler.to_latex() #21673

This allows Styler.to_latex to also render \cline to separate sparse MultiIndex rows according to user input. Tests are also included to demonstrate functionality with hidden rows and hidden index levels.

Note that DataFrame.to_latex also uses \cline but it is forced in certain cases without options.

midx = pd.MultiIndex.from_product([["A", "-", "B"], [0], ["X", "Y"]], names=["lvl 0", "lvl 1", "last lvl"])
df = pd.DataFrame([[1, "pig"], [2, "coin"], [99, ""], [99, ""], [3, "sky"], [4, "pie"]], 
                  index=midx, columns=["int", "str"])
styler = df.style
styler.hide([("-", 0, "X"), ("-", 0, "Y")])
styler.hide(level=[1,3])
print(styler.to_latex(clines="all;index", hrules=True, multirow_align="t"))

	all	skip-last
index
data

Default render without clines:

[jreback]

@meeseeksdev backport 1.4.x

[jreback]

thanks @attack68

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