Unnecessary GL states call at "end of Renderer:draw" frame(up and above 18 gl state calls)

[Kuranes]

repro steps:
run a sample, capture a glTrace with gl inspector, see all call after the last gl.DrawElement to end of frame.

Comment State.apply here:

osgjs/sources/osgViewer/Renderer.js

Line 193 in a4587df

state.apply();

re-run same sample, capture a gltrace with glinspector.

And see that all the unnecessary calls are removed.

All samples/tutorial runs well without but "multiple viewer" sample

But it shouldn't be enabled in all the other use case, as GL call are very costly (and pollute gl traces)

In case of FOG sample, half the gl call are unnecessary (18/36).

if use case is to "revert webgl state to a neutral state", better just share the "lastapplied" states thing between frame/viewers as it would allows for even fewer states on usecase where states are always the same during and between frames/viewers.)

[cedricpinson]

Since a lot of stuff has been fixed to avoid duplicate state, it should be fixed