[no sq] Fix ECF_D32 support in ogles2 video driver

[grorp]

fixes #15395

OES_depth32 only talks about support for render buffers, not textures, so it's not relevant here: https://github.com/KhronosGroup/OpenGL-Registry/blob/main/extensions/OES/OES_depth32.txt

This fixes the scene being black with "video_driver = ogles2" and "enable_post_processing = true" on my desktop computer.

To do

This PR is a Ready for Review.

How to test

ogles2 on Android: things should work
ogles2 on desktop: things should work

[sfan5]

code looks good, no change on my pc

[sfan5]

random thing I found on SO:

GL_DEPTH_COMPONENT32 is probably overkill, and as of 4.5, isn't a required format for OpenGL implementations to support (though 16 and 24 bit ones are). Consider that higher resolution depth buffers may not be as performant.

maybe we should be preferring ECF_D24S8 because do we really need 32-bit precision for the depth buffer?
even better we can add ECF_D24 to avoid wasting memory on a stencil buffer we don't need.

edit: also here:

Another great trick at the cost of some performance is to use a higher precision depth buffer. Most depth buffers have a precision of 24 bits, but most GPUs nowadays support 32 bit depth buffers, increasing the precision by a significant amount. So at the cost of some performance you'll get much more precision with depth testing, reducing z-fighting.

[grorp]

maybe we should be preferring ECF_D24S8 because do we really need 32-bit precision for the depth buffer?
even better we can add ECF_D24 to avoid wasting memory on a stencil buffer we don't need.

Luckily I can declare this "out-of-scope for this PR" 😅