LaTeX: refactor sphinxShadowBox to allow colors for frame and shadow

[jfbu]

This adds possibility of colors for the "shadowed" box used for the topic and contents directives.

No change to existing output, as default colors left to black.

Here is an example of use:

(the box allows pagebreaks as formerly, this is not shown here)

The example uses:

latex_elements = {
    'sphinxsetup': """%
  shadowrule=2pt,%
  shadowsize=6pt,%
  shadowShadowColor={RGB}{170,170,170},%
""",
}

in conf.py.

edit. I messed up horizontal width, will fix later to maintain behaviour as current. Well I wll never understood what went wrong, so I redid it entirely, and the code is much closer to current one.

Here is an example of use with a page break, to show no color leaks:

Topics
------

Hello

.. raw:: latex

   \rule{1cm}{1cm} \hrulefill \rule{1cm}{1cm}

.. topic:: Some topic

   .. raw:: latex

      \begingroup\color{blue}

   Some contents possibly very long, we added color via raw latex, to check
   nothing bad happen even at at page break. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. Some contents possibly very long. Some
   contents possibly very long. 

   .. raw:: latex

      \endgroup

.. raw:: latex

   \rule{1cm}{1cm} \hrulefill \rule{1cm}{1cm}

with conf.py:

latex_elements = {
    'sphinxsetup': """%
  shadowrule=10pt,%
  shadowsize=20pt,%
  shadowShadowColor={RGB}{170,170,170},%
  shadowBorderColor={RGB}{255,0,0},%
""",
}

[tk0miya]

LGTM!

[jfbu]

Thanks as always for reviewing @tk0miya! I thought about adding interface for coloring the contents but it is now available to Sphinx user via something such as

\protected\def\sphinxstyletopictitle #1{\leavevmode\color{red}% color for contents
                                \textcolor{green}{\textbf{#1}}% colored title
                                \par\medskip}

(btw I don't think the \protected is needed here but it is currently present in sphinxlatexstyletext.sty).
With current 5.x, the above code would have leaked the text color (red in this example) to the shadow and part of the frame. Now with this PR merged the above user configuration will modify only contents color, so it can be used safely. Anyhow, contents topic boxes contain hyperlinks which have their own coloring...and above user config will impact only color of the box title from contents directive. Text paragraphs color will be changed by above user config for topic boxes.

Now merging...

[jfbu]

This got refactored at #10648 with new names aside.topic_border-TeXcolor and aside.topic_box-shadow-TeXcolor and addition of possibility of having a background color aside.topic_background-TeXcolor.

[jfbu]

was superseded by #10648