Propagate QSvgExtraStates variables to pattern and mask elements

To avoid exceeding the maximum number of nested renderable nodes, these
values must be propagated to the pattern and mask elements, which create
a fresh QSvgExtraStates before rendering their child elements. Moreover,
the trustedSource flag was also left out when it was introduced to
QSvgExtraStates.

Amends 16119ddc0f8a39a7131d95715c7d9c01e428819d.

Task-number: QTBUG-145916
Pick-to: 6.12 6.11 6.10 6.8
Change-Id: I141edbe911c2ab6929c8ebbb476be26dca6de295
Reviewed-by: Samuel Gaist <samuel.gaist@idiap.ch>
Reviewed-by: Eskil Abrahamsen Blomfeldt <eskil.abrahamsen-blomfeldt@qt.io>