feat: Implement graph widget in OC tab

[In-line]

[In-line]

@ilya-zlobintsev I'm in the middle of refactoring and adding throttle visualization, but feel free to review WIP impl too

[In-line]

New look & feel

[In-line]

@ilya-zlobintsev feel free to review

[ilya-zlobintsev]

This is a very cool addition, but there are some considerations:

• The graph currently shows GPU usage and temperature on a single chart. This works fine since the values have a similar range, but in the future it could be useful to have graphs for clockspeed, voltage or power usage - those would have to be separate. Not yet sure how that should look
• IMO the OC page is getting kind of crowded, I think it would be best to hide the graph behind something like an expander by default, like it's done for power states. Alternatively, and considering point 1, there could be a dedicated popout window specifically for real-time graphs that the user can open on the side as needed. It could also contain more graphs in the future.
• The graph is currently drawn on a white background - ideally it would look like something that tries to integrate with the rest of the widgets by following the GTK theme, but I am not sure if that's feasible to implement. Though if the popup window is implemented this isn't as much of an issue, as there would be a separate window that's mostly white graphs, and the main window without them. Another solution could also be having dark/light modes for the graph, and selecting one based on system settings.
• Passing data to the plot via a json isn't the best. It should be possible to set it directly, but probably needs to be connected to the widget manually instead of relying on derived properties + bindings in the template
• I see that you had to downgrade gtk-rs for this. Probably can't do much about it until plotters-cairo gets updated

I'm also gonna need to read up some theory to understand how the cubic spline works 🙂

But overall this would be a very useful thing to have. Typically I use amdgpu_top for real-time monitoring, but it would be nice to have some historical data in LACT too, especially when you're over/underclocking and want to see the impact.

[ilya-zlobintsev]

@In-line I've made another PR based on this one, implementing most of the things mentioned in the previous comment. Please take a look at it when you can: #301

[ilya-zlobintsev]

I'm going to close this PR as it has been superseded by #301 (feel free to leave your thoughts about further improvements)