WebGL2 Graphics device creation with stencil: false breaks depth scene grab

[heretique]

Description

When WebGL2 device creation is done with stencil: false and post effects are enabled, depth scene grab starts failing as framebuffers don't match when doing WebglGraphicsDevice.copyRenderTarget.

This has been observed on Edge/Chrome and Firefox.
There are a lot more details in this forum thread (conclusion towards the end):
https://forum.playcanvas.com/t/depth-issues-when-enabling-a-post-process-effect/33024/20

Steps to Reproduce

1. load Post Effects example
2. add the line stencil: false to const gfxOptions at line 28
3. open the dev console
4. switch to WebGL2 as active device.
5. Example breaks and notice warnings in the console: [.WebGL-0x104005b3400] GL_INVALID_OPERATION: Depth/stencil buffer format combination not allowed for blit.

Note

This can be reproduced with the Ground Fog example as well only on FIrefox without the need for post effects to be enabled, just follow the same steps and notice similar warnings in the console WebGL warning: blitFramebuffer: Depth buffer formats must match if selected. and the depth debug view is white.