[Feature Request] [SPIRV] Support `SPV_EXT_shader_invocation_reorder`

Is your feature request related to a problem? Please describe.

https://github.com/microsoft/DirectXShaderCompiler/issues/6994 for the older SPV_NV_shader_invocation_reorder was previously closed as blocking on https://github.com/microsoft/hlsl-specs/pull/277 to add a SER proposal to HLSL first. Now that that's in, and the SPIR-V extension was promoted to EXT, would it be possible to target SPV_EXT_shader_invocation_reorder in SPIR-V?

Describe the solution you'd like
When dx::HitObject is used in code that is compiled to SPIR-V with dxc -spirv, the SPV_EXT_shader_invocation_reorder extension is used.

Describe alternatives you've considered
The Vulkan VK_NV_ray_tracing_invocation_reorder extension mentions how to use SPIR-V intrinsics to achieve this, which should trivially translate to SPV_EXT_shader_invocation_reorder even if a manual conditional implementation needs to be added next to existing dx::HitObject usage.

Additional context
Add any other context or screenshots about the feature request here.

Start by tracing how dx::HitObject is lowered when dxc -spirv is used, then compare that path with the Vulkan HLSL mapping and the SPV_EXT_shader_invocation_reorder specification linked in the issue. Done means code using dx::HitObject emits the EXT extension rather than relying on the older NV behavior, with compiler coverage for the generated SPIR-V.