Readd extra brightness feature as optional setting

[Pawloland]

Readd extra brightness feature added in #2416 and removed in c1a2ae8
as optional setting and fix brightness icon animation on gesture in a player.

In the meantime the zoom feature was added, and it is incompatible with the brightness filter in the current form. When the filter is disabled in settings (it is by default), then zooming works fine. With filter enabled, only the 3 preprogrammed modes are working.

[LagradOst]

I believe that using a GL shader for extra brightness is a bit overkill. Given that it is now incompatible with several features and causes lag, another approach might be needed. Given that the entire shader is:

gl_FragColor = vec4((textureColor.rgb + vec3(brightness)), textureColor.w);

I think that you can achieve the exact same result using a transparent white texture. The only problem might be if the source video is also transparent, but I think that is an edgecase worth the feature compatibility and runtime cost. Just add something in the style of:

<View
            android:id="@+id/brightness_alpha_overlay"
            android:alpha="extra brightness programmatically"
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:background="@color/white" />

Then the android OS can do the alpha blending and get the same result as the shader.

Also see: #2416 (comment)

[Pawloland]

It now uses simple view overlay and supports changing scaling with a button or by pinch to zoom&pan. Pip window resizing also works correctly. Ready for review and merge on my side.