Added a QSpinBox to adjust granularity while doing transforms

Summary:
The patch adds a QSpinBox to the transform tool options to adjust the granularity while doing transforms.

This patch fixes real transformation granularity only, preview
granularity will be solved in the following patches.

CCBUG:344210

Reviewers: #krita, rempt, dkazakov
Reviewed By: #krita, dkazakov
Subscribers: #krita
Tags: #krita

Differential Revision: https://phabricator.kde.org/D17660