Prefix all remaining OpenGL-specific classes with "GL" in name

[frenzibyte]

First steps towards supporting Veldrid, need to have all OpenGL-specific classes prefixed with GL to not conflict in names with the upcoming Veldrid variants. Few notes:

• GLLinear{Buffer,Batch} reads a bit weird given the double L in the name, but not sure if it should be renamed.
• VideoTexture has been renamed to VideoTextuerGL and also been moved to the OpenGL.Textures namespace, instead of its original place (Videos).
• IVertexBuffer has also been prefixed as it's currently internal and OpenGL-specific, but it could potentially be moved out if we decide to have a base Renderer/VertexBatch class which makes use of this interface.

[peppy]

I'd prefer GL rather than OpenGL for brevity. Also optionally, it could be a suffix in all cases similar to VideoTextureGL. Need more opinions on that.

[frenzibyte]

I was under the thought that the “GL” suffix was used to indicate that the class isn’t directly an inheritor of an interface/class with the same name (i.e. TextureGL looks like it’s own class, while GLTexture/OpenGLTexture sounds like it inherits from Texture).

Bit of a weak argument though, and I’ve already opted to call the Veldrid one as VeldridTexture rather than TextureVd anyways.

[smoogipoo]

“GL” suffix was used to indicate that the class isn’t directly an inheritor

There's nothing special about the naming. I agree with using "GL".

Also optionally, it could be a suffix

Hmm. We typically don't suffix things in o!f/lazer, as opposed to stable. Between VertexBufferVeldrid/VertexBufferVd and VeldridVertexBuffer/VdVertexBuffer, I think I prefer the latter.

[peppy]

Prefix is fine. "Vd" feels weird so I'd prefer using "Veldrid".