Missing SPV_EXT_replicated_composites validation

@kpet there is no validation for this extension

- I imagine this would go in the `ValidateConstantComposite()` function
- Also see a case in `CommonDebugInfoDebugGlobalVariable` where `OpConstantComposite` is allowed
- Can this be used to set the Workgroup size? We have checks in `ValidateWorkgroupSizeAtDefinition`
