chooseSpriteProgramType(): Add missing PixelFormat::RGB8

[aismann]

Describe your changes

see diff

1. Missed: PixelFormat::RGB8 returns POSITION_TEXTURE_COLOR
2. Maybe Im wrong, but I think RGBA8 should return "POSITION_TEXTURE_COLOR_ALPHA_TEST"

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[aismann]

@halx99
I also think it's time to rename ‘POSITION_TEXTURE_COLOR_ALPHA_TEST’ to ‘POSITION_TEXTURE_COLOR_ALPHA’
and all related files (shaders). (Before it gets forgotten).

[halx99]

@halx99 I also think it's time to rename ‘POSITION_TEXTURE_COLOR_ALPHA_TEST’ to ‘POSITION_TEXTURE_COLOR_ALPHA’ and all related files (shaders). (Before it gets forgotten).

No, the semantic not same: https://github.com/axmolengine/axmol/blob/dev/axmol/renderer/shaders/positionTextureColorAlphaTest.frag

[halx99]

And this PR incorrect

[aismann]

And this PR incorrect

I close this PR.