tests: SVGAnalyzer: extend 'make_from_dot' method and use in test_svg_analyzer

tests: SVGAnalyzer: extend 'make_from_dot' method and use in test_svg_analyzer

This change adds support to the SVGAnalyzer for saving a
copy of the Graphviz version and build ID which are needed to exactly
re-create the SVG document.

Upcoming commits will extend the SVG analyzer's ability to handle new
SVG attributes and add new test cases verifying its ability to
re-create correct SVG containing those attributes. This change will
facilitate the creation of those tests and keep the code DRY.