[GSoC] Query History Upgrade

Hi Hackers,

Please find attached a patch including new features for the Query History
as follows:

- Integration with updatable resultsets: Queries generated by pgAdmin
during Save Data operations are now shown in the history panel, including
transaction control queries.
- Source indication: The source of each query in the history panel is
indicated using an icon corresponding to the toolbar (Save Data, Execute,
Explain, Commit, Rollback & View/Edit).
- Allow showing/hiding queries generated internally by pgAdmin using a
toggle button.
- Some refactoring in save_data_changes.py

The patch includes the code for the feature, added feature tests and
documentation updates.
Please review !

Thanks. Regards.

-- 
*Yosry Muhammad Yosry*

Computer Engineering student,
The Faculty of Engineering,
Cairo University (2021).
Class representative of CMP 2021.
https://www.linkedin.com/in/yosrym93/