Android: Expose color space settings

[t895]

As per @Filoppi 's request

HDR settings are not included because HDR support is not present in the app yet.

[Filoppi]

Good stuff.
I checked how color managment works in Android:
https://source.android.com/docs/core/display/color-mgmt
that doc confirms that Dolphin is already color managed when using Vulkan on Android (see VK_COLOR_SPACE_SRGB_NONLINEAR_KHR), as in, the colors sent by the emulator to the OS will be interpreted as sRGB (gamut and gamma) and mapped to whatever color space the display is using, so they will always be accurate. I don't think OpenGL ES is color managed because we don't specify the output as sRGB.
This implies there's no need to expose the custom gamma settings like it's needed on Windows/PC (Windows is not color managed at all atm).
All stuff regarding these two options can be removed from this PR:

color_correction.bSDRDisplayGammaSRGB = Config::Get(Config::GFX_CC_SDR_DISPLAY_GAMMA_SRGB);
color_correction.fSDRDisplayCustomGamma = Config::Get(Config::GFX_CC_SDR_DISPLAY_CUSTOM_GAMMA);

GFX_CC_SDR_DISPLAY_GAMMA_SRGB can be left at default (true) as it already is, because the OS will always interpret the image as sRGB.
The "Correct Gamma" option is the only one that should stay, and possibly, as an extra, the "Game Gamma" setting, but I wouldn't bother if you don't want.

[t895]

Everything should be in order now

[JosJuice]

Using Any feels kind of ugly. What do you think of using an algebraic data type (using sealed)? Then it would be clearer what types can be returned, and you would be able to use when in place of if (item is FloatSliderSetting).

[t895]

I like that a lot actually. Pushing that change now.

[JosJuice]

What you implemented isn't what I suggested, but I suppose what you implemented works too.

[Filoppi]

LGTM