Support showing mpv statistics and possibly key binding via scripts

[John-He-928]

This is actually a bug in official IINA that not (fully) fixed I think. The official issue: https://github.com/iina/iina/issues/1053

The mpv-stats.lua script is not able to add key bindings to IINA, so the statistics feature in mpv is somewhat unusable. IINA official gives a workaround that add key bindings manually to switch pages. I don't think this is a perfect solution. Also, the page 2 of the statistics, frame timing, don't shown up even with a key binding. The frame timing page is very useful when debugging video filters or custom shader scripts.

What you want IINA to do:

• Support showing frame timing statistics page.
• Support key bindings from scripts, if possible.

What IINA does currently:

When switching to frame timing page, it shows no contents.

Why you think this should be added:

The frame timing page is very useful when debugging video filters or custom shader scripts.

Examples of other projects that have something similar: The mpv official manual page: https://mpv.io/manual/master/#stats