Bug 1593381 - Port APZCTreeManagerGenericTester.ScrollablePaintedLayers to use WR inputs. r=hiro

Part of this test had to be removed because it performs an operation,
"change a FrameMetrics which is shared with another Layer", which
the WR data structures do not support, and which does not need
test coverage (since production code cannot do it either).

Differential Revision: https://phabricator.services.mozilla.com/D124297