Properly trigger repaint for sofware cursor

Summary:
When the cursor changes the old and the new cursor geometry needs to
be repainted. Also when the cursor image changes a repaint of old and
new geometry is needed.

To support this the current cursor geometry is tracked instead of just
the cursor position. From the cursor position it's not possible to get
to the cursor geometry once the cursor image or hotspot changes, thus
the complete geometry needs tracking.

CCBUG: 356328

Reviewers: KWin, Plasma on Wayland

Subscribers: plasma-devel, kwin

Tags: Plasma on Wayland, KWin

Differential Revision: https://phabricator.kde.org/D2023