Add slider menu item, configuring on-screen controls size

[Vankata453]

Adds the ItemSlider menu item. It allows selecting an integer value between a minimum and a maximum value. It can be used with the left mouse button, left/right arrow keys or scroll wheel. The slider step (interval between values when using the arrow keys or scroll wheel) is configurable from "Options" -> "Advanced".

The sound volume, music volume and flash intensity options now utilize a slider. The on-screen controls scale option was added back in "Options" -> "Controls" and utilizes a slider as well.

https://github.com/user-attachments/assets/63888af9-24da-43a2-a44c-52e24aa057f7

Additionally:

• The on-screen controls toggle has also been re-added in "Options" -> "Controls".
• The on-screen controls configuration values were changed to allow for broader scale customization.

Closes #3010. Closes #3033.

[Vankata453]

Just make sure there's a way to specify the step.

What step?

[MatusGuy]

The step is the interval between values. For example, if the step is 5, each time you press the right key, instead of increasing by 1 it increases by 5. And when using a cursor it snaps to the right place.

[Vankata453]

Sure, will make an option for it.

[tobbi]

I haven't tested it yet but... Many of the sliders in UI Frameworks have the option of increasing / decreasing when the user hovers over the slider and uses the mouse wheel. Any plans on implementing that?

[Vankata453]

Will do, I forgot they had that.

[Vankata453]

Added customizable slider steps and scroll wheel support.

[Thatstinkyguy]

@Vankata453 Awesome work! Will these features be added to the Android version?

[Vankata453]

Will these features be added to the Android version?

After this is merged, they will.

[tobbi]

/home/runner/work/supertux/supertux/src/gui/item_slider.cpp:90:96: error: implicit conversion from 'int' to 'float' may lose precision [-Werror,-Wimplicit-int-float-conversion]
        *m_value = static_cast<int>(((mouse_pos.x - m_slider_x) / SLIDER_WIDTH) * (m_max_value - m_min_value)) + m_min_value;
                                                                                ~  ~~~~~~~~~~~~^~~~~~~~~~~~~
/home/runner/work/supertux/supertux/src/gui/item_slider.cpp:114:96: error: implicit conversion from 'int' to 'float' may lose precision [-Werror,-Wimplicit-int-float-conversion]
        *m_value = static_cast<int>(((mouse_pos.x - m_slider_x) / SLIDER_WIDTH) * (m_max_value - m_min_value)) + m_min_value;
                                                                                ~  ~~~~~~~~~~~~^~~~~~~~~~~~~
2 errors generated.