Fix front face definition

[hi-ogawa]

This will fix the shadow artifact reported in this issue #11848 (the first issue of the two issueses reported there).

I will explain a bit more detail even though the commit is so small.
I found that the first call of RasterizerSceneGLES3::_render_list (more specifically, _render_geometry and glDrawXXX from that function) uses front face mode GL_CCW (counter clock wise) since that's the default value and glFrontFace(GL_CW) is only called at the end of the RasterizerSceneGLES3::_render_list.
This led to the opposite front face definition when we generate shadow map for the first time in the application lifetime, which causes shadow artifact as in that issue.
Another thing to note is that shadow map is not re-drawed in every frame when scene is static, so the first wrong front face shadow map is continued to be used in that case.

I figured this type of one-time gl state setup can be in RasterizerSceneGLES3::initialize, so that's what my PR is.

[groud]

Ok, this looks good to me and pretty straightforward. Merging.