Auto merge of #85578 - RalfJung:alloc-mem-extra, r=oli-obk

CTFE get_alloc_extra_mut: also provide ref to MemoryExtra

This would let me use mutable references in more places in Stacked Borrows, avoiding some `RefCell` overhead. :)

r? `@oli-obk`

compiler/rustc_mir/src/interpret/memory.rs

@@ -673,8 +673,9 @@ pub fn get_mut<'a>(
     pub fn get_alloc_extra_mut<'a>(
         &'a mut self,
         id: AllocId,
-    ) -> InterpResult<'tcx, &'a mut M::AllocExtra> {
-        Ok(&mut self.get_raw_mut(id)?.0.extra)
+    ) -> InterpResult<'tcx, (&'a mut M::AllocExtra, &'a mut M::MemoryExtra)> {
+        let (alloc, memory_extra) = self.get_raw_mut(id)?;
+        Ok((&mut alloc.extra, memory_extra))
     }
 
     /// Obtain the size and alignment of an allocation, even if that allocation has