Addition of compatibilty tests for `printf()`.
While doing this I found some differences in the current implementation,
so this fixes those too.
Closes#3438
When adding tests for extensions, please follow these guidelines:
Tests that verify the internal logic or behavior of a particular extension should go into cli_tests/extensions.py.
Tests that verify how extensions interact with the database engine, such as virtual table handling, should be written
in TCL (see vtab.test as an example).
To check which extensions are available in TCL, or to add a new one, refer to the tester.tcl file and look at the extension_map.
2b59863447