tests: Add testdatatable

tests: Add testdatatable

Add a GtkColumnView scrolling performance test similar to the one used
previously in https://gitlab.gnome.org/GNOME/gtk/-/issues/3334.

The test creates a table with 20 columns and 10,000 rows and scrolls it
to a random position every frame, while measuring the frame times.

There is a commandline flag to pick the cell widget between none (for
benchmarking raw column view scrolling) and various label types. There
is also a commandline switch to disable automatic scrolling in case a
manual assessment is desired. Finally, there's an argument for
controlling the number of columns.