wg_engine: artifacts bugs fix

Fix borders artifacts by changing sampling clamp method from repeat to clamp

#3528

svg: fix memory leak++

sw_engine: thread safety++

resolved a thread sanitizer report

svg: thread safey++

root is not thread safety resource,
must be guarded with LoadModule::read() call.

a regression 10d36c2
during main dev.

bump up version v0.15.16

sw_engine: improve drop shadow stabilization

Injected missing buffer swapping to
preserve non-direct drawing operations.

issue: #3814

wg_engine: fix shape aabb transfrom

Each shape has two types of bounding boxes: one from the original path and one from its transformed version.
If the transformation changed, the aabb wasn't updated, which resulted in effects being applied to the wrong area of he screen.
Now, if the transformation changes, the aabb is recalculated.

#3762

infra: --shutdown build warning on macos

bump up version v0.15.15

lottie: properly copy the colorstop data

previous logic only supported the shallow copy,
deep copy version is now implemented.