applets/clipboard: add privacy mode
Reason for the change
When it's enabled, any new clips will not be saved to the history.
Test plan
- Enable privacy mode in the widget
- Copy some text
- The copied text does not appear in the history
- Disable privacy mode
- Copy some text
- The copied text appears in the history
Screenshots or screen recordings
Bugs fixed
FEATURE: 427724 FIXED-IN: 6.2