Mutable bind groups #5186

"Bind group updates" was one of the things we listed during the 2024-10 F2F Milestone 1 prioritization discussion. But I don't think we really have an issue filed for it.

• It was discussed as a possible solution in Efficient Per-Frame/Transient Bind Groups #915. But it doesn't seem we got into that much detail on it, so this issue is basically an alternative to that one (transient bind groups).
• We would like if it's possible to do this in the middle of a command buffer. Investigation needed into what this requires (e.g. VK_KHR_push_descriptor?, EDIT: VK_EXT_descriptor_buffer?).
• I recall another proposal for creating a new bind group that duplicates an existing one with changes. That would avoid synchronization issues.
• IIRC this is related to Investigation: Bindless resources #380.
• It would address Can importExternalTexture requirements be relaxed? #5172.
• It solves some similar problems but is most likely separate from Add inherited Bind Groups to Render Bundles. #5185