Allow Clone Brush to reset origin after every stroke

Summary:
This commit introduces the behaviour of Clone Brush
that allows for always starting a new stroke
as if the offset wasn't set yet, which means it always
starts from the same source/origin point.
Usecases: painting multiple leaves, flowers, crosses etc.
in less regular way than what could be created with regular
Clone Brush.

BUG:402559

Test Plan:

• save and load brush with and without the new option enabled
• use the same brush with and without the new option enabled
• use both versions without setting the origin
• switch between enabled and disabled option after setting the origin
• check whether the tooltip works

Reviewers: Krita, dkazakov

Reviewed By: Krita, dkazakov

Subscribers: dkazakov

Tags: Krita

Differential Revision: https://phabricator.kde.org/D20653