Summary:
The screenshot methods to blit the screen so far did not capture the
cursor image. But sometimes it is useful to also capture the cursor
image.

This change extends the exported methods to take an optional bool
argument whether to capture the screen. The default is not changed and
still not captures the cursor.

Reviewers: #kwin, #plasma_on_wayland

Subscribers: plasma-devel, kwin

Tags: #plasma_on_wayland, #kwin

Differential Revision: https://phabricator.kde.org/D3118