Fix: Vector Stroke Style propagating to other objects

SvgContext spilled caused by copying pointer instead
of copying values for stroke.

All TestSvgParser pass. Attached bug files render as expected.
should be safe to port to krita 4.2

Bug:407683

BACKPORT:krita/4.2
(cherry picked from commit e6b80a857c9c9aadd3900767e9293a3f26baf01e)