[MSSA][MDA] Incorrect handling of single iteration scoped alias metadata across backedge

```llvm
; RUN: opt -passes='early-cse' -S < %s

; Assume %p and %q are the same pointer
define i32 @f(ptr %p, ptr %q) {
entry:
store i32 7, ptr %p, align 4
br label %loop

loop:
%i = phi i32 [ 0, %entry ], [ %i.next, %latch ]
call void @llvm.experimental.noalias.scope.decl(metadata !2)
%c = icmp eq i32 %i, 0
br i1 %c, label %write, label %exit

write:
store i32 42, ptr %q, align 4, !alias.scope !2
br label %latch

latch:
%i.next = add nuw nsw i32 %i, 1
br label %loop

exit:
%v = load i32, ptr %p, align 4, !noalias !2
ret i32 %v
}

!0 = !{!0}
!1 = !{!1, !0}
!2 = !{!1}
```

This folds to return 7, however the value 42 is stored in the loop. There is no UB because the write and the read are on different iterations, passing through noalias.scope.decl in between.

The issue also occurs with `-passes=gvn` via MDA.

Based on https://github.com/llvm/llvm-project/pull/222686#issuecomment-5647760268.

Start by running the provided opt reproducer with early-cse and then with gvn to compare the behavior through MDA. Trace how scoped alias metadata and llvm.experimental.noalias.scope.decl are handled across the loop backedge; done means the passes no longer fold this case to return 7, while preserving the valid cross-iteration store and load behavior.

Written by the indexing model from the issue text.