Chrome still tends to use ES2 contexts for most rasterization. This is a
problem when trying to use FP16 IOSurfaces for rendering HDR because
GL_RGBA16F is not renderable in ES2. Since a surface is always
renderable, allow rendering to any textures with a bound surface.

Update the tests to verify that ES3 formats can be used with ES2
contexts.

Add tests for RGBA16F IOSurfaces.

BUG: chromium:1103112
Change-Id: I9e8c082fc97a0e072289b097e71fc944988d4872
Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2307454Reviewed-by: Jonah Ryan-Davis <jonahr@google.com>
Reviewed-by: Geoff Lang <geofflang@chromium.org>
Commit-Queue: Geoff Lang <geofflang@chromium.org>