Use Inkscape File -> clean up document functionality to remove SVG bloat.
This does not even remove all Inkscape specific metadata, but already
hugely reduces file size (and complexity).
before: 1.432.192 bytes, after: 633.535 bytes
It seems this function was previously called "Vacuum defs" in Inkscape,
and the savings we see are in large part due to removal of unused defs.
In some files it also changes the way paths are defined, but without
obvious visible changes.
The files still contain Inkscape metadata like the window size, version
and workspace position that could be removed without losing useful SVG
Also note that for the file publicdomain/Information_icon.svg as well as
the layout_* files this process would actually increase file size as
Inkscape adds additional metadata. Hence that file is not changed.