Resolve depth buffer in mobile renderer when required

[BastiaanOlij]

This PR fixes a long standing issue with the mobile renderer when using MSAA. The subpass logic never had an option for resolving the MSAA depth buffer to a normal depth buffer.
This meant that:

• reading from depth texture broke as the depth texture being copied to the back buffer was empty
• when using an external depth texture (XR) the depth texture wasn't populated

This PR does rely on the VK_KHR_depth_stencil_resolve extension. This has been core since Vulkan 1.2 and was a KHR extension in Vulkan 1.0/1.1 and may not be supported on all GPUs.

Todos:

• consider whether we want a fallback solution when the resolve extension is not available or adjust the back buffer copy to read from the MSAA buffers
• add check that the MSAA depth buffer and normal depth buffer have compatible formats to enable the resolve
• implement fallback if the XR solution can't provide a compatible buffer

[BastiaanOlij]

I need to do some more testing but I think this also solves #78544

[Saul2022]

I think there should be 100% a fallback as the mobile renderer works better on older pc and it also has to support mobile, which nowadays it vulkan support is not the best.

[BastiaanOlij]

@Saul2022 agreed though I'd like to mark all the "todos" for future PRs. This is an important fix I'd like to get into 4.1 and the fix window closes Monday. As currently resolving doesn't work plus we have a number of validation errors that are solved by this, this is a step forward and shouldn't break anything that isn't already broken.

@clayjohn @akien-mga I'm marking this for review due to the above reason if you guys are ok with that.

[akien-mga]

As discussed on chat, let's not rush it now, but this is a good candidate for 4.1.1 once finalized and merged for 4.2.

[Calinou]

Does this resolve #78785?

[BastiaanOlij]

@Calinou I don't think so, but that is one I need to find time for

[LeandroSQ]

Is this still getting merged? I also got the same issue on my XR project so I wonder if there are any workarounds too.