Proposal - 3.0 Managed Chain Changes

[Khitiara]

Summary of the PR

A proposal for changes, some of them breaking, to the managed chain utilities for 3.0.

Related issues, Discord discussions, or proposals

As discussed in discord with the SilkX team.

[Perksey]

Can you add .md to the filename

[Perksey]

No pre-WG comments here

[curin]

No comments from me, either, but VK is also not my area of expertise, so I'm just going off of the proposal working as explained.

[Perksey]

• We believe that the chain abstractions break down significantly anyway when used as an output with layers that can possibly inject additional PNexts that aren't reflected in these abstractions.
• As a result, this chain abstraction only really works with inputs in every case.
• UntypedHeadPtr being changed from BaseInStructure is contrary to this assumption.
• Why is it IStructuredType instead of ITypedStructure? Changing this doesn't affect too much, but leaving it as is doesn't affect too much either.
• 3.0 is the opportunity to fix long-standing issues like this as it's already massively breaking, so we can do silly changes like this.
• IStructuredType is already broken with this proposal, so let's just rename it anyway.
• We believe that IBaseStructure is probably the most sensible name given how Vulkan names this.
• Everything else looks fine, approved notwithstanding the above.