Remove manual render state setting

Nested render calls now automatically restore the correct render state from the stack.

getRenderState/setRenderState are not part of the public API so they can be safely removed from WebGLRenderer.

src/renderers/WebGLRenderer.js

@@ -1768,18 +1768,6 @@ function WebGLRenderer( parameters ) {
 
 	};
 
-	this.getRenderState = function () {
-
-		return currentRenderState;
-
-	};
-
-	this.setRenderState = function ( renderState ) {
-
-		currentRenderState = renderState;
-
-	};
-
 	this.getRenderTarget = function () {
 
 		return _currentRenderTarget;

src/renderers/webgl/WebGLCubeMaps.js

@@ -42,7 +42,6 @@ function WebGLCubeMaps( renderer ) {
 
 						const currentRenderList = renderer.getRenderList();
 						const currentRenderTarget = renderer.getRenderTarget();
-						const currentRenderState = renderer.getRenderState();
 
 						const renderTarget = new WebGLCubeRenderTarget( image.height / 2 );
 						renderTarget.fromEquirectangularTexture( renderer, texture );
@@ -50,7 +49,6 @@ function WebGLCubeMaps( renderer ) {
 
 						renderer.setRenderTarget( currentRenderTarget );
 						renderer.setRenderList( currentRenderList );
-						renderer.setRenderState( currentRenderState );
 
 						texture.addEventListener( 'dispose', onTextureDispose );